ÁñÁ«ÊÓƵ

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Filed Pursuant to Rule 424(b)5
Registration No. 333-186702

PROSPECTUS SUPPLEMENT

(To Prospectus dated February 15, 2013)

$275,000,000

2.75% Senior Convertible Notes due 2019

Interest payable April 1 and October 1

Issue price:

We are offering $275,000,000 aggregate principal amount of 2.75% Senior Convertible Notes due April 1, 2019 (the “notes”). The notes will bear interest at a rate of 2.75% per year, payable semiannually in arrears, on April 1 and October 1 of each year, beginning on October 1, 2013. The notes will mature on April 1, 2019.

Holders may convert their notes at their option at any time prior to the close of business on the business day immediately preceding October 1, 2018 only under the following circumstances: (1) during any calendar quarter commencing after the calendar quarter ending on June 30, 2013 (and only during such calendar quarter), if the last reported sale price of the common stock for at least 20 trading days (whether or not consecutive) during the period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day; (2) during the five business day period after any five consecutive trading day period (the “measurement period”) in which the trading price (as defined herein) per $1,000 principal amount of notes for each trading day of the measurement period was less than 98% of the product of the last reported sale price of our common stock and the conversion rate on each such trading day; (3) if we call the notes for redemption; or (4) upon the occurrence of specified corporate events. On or after October 1, 2018 until the close of business on the second scheduled trading day immediately preceding April 1, 2019, holders may convert their notes at any time. Upon conversion, we will pay or deliver, as the case may be, cash, shares of our common stock or a combination of cash and shares of our common stock, at our election, as described in this prospectus supplement.

The conversion rate will initially be 39.5491 shares of common stock per $1,000 principal amount of notes (equivalent to an initial conversion price of approximately $25.29 per share of common stock). The conversion rate will be subject to adjustment in certain events described in this prospectus supplement but will not be adjusted for accrued interest. In addition, following certain types of fundamental changes, as described in this prospectus supplement, or a notice of redemption, we will, in certain circumstances, increase the conversion rate for a holder who elects to convert its notes in connection with such fundamental change or notice of redemption, as the case may be.

We may not redeem the notes prior to April 5, 2017. On or after April 5, 2017, we may redeem for cash any or all of the notes, at our option, if the last reported sale price of our common stock for at least 20 trading days (whether or not consecutive) during any 30 consecutive trading day period ending within 5 trading days immediately preceding the date on which we provide notice of redemption exceeds 130% of the applicable conversion price on each applicable trading day. The redemption price will equal 100% of the principal amount of the notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date.

If we undergo a fundamental change (as defined herein), holders may require us to repurchase the notes in whole or in part for cash at a price equal to 100% of the principal amount of the notes to be purchased, plus any accrued and unpaid interest to, but excluding, the repurchase date.

The notes will be our senior and unsecured obligations and will rank equally in right of payment with all of our existing and future senior indebtedness and senior in right of payment to all of our existing and future subordinated indebtedness. The notes will be structurally subordinated to any of our existing and future secured indebtedness to the extent of the value of the collateral securing such indebtedness, including all borrowings under our senior secured revolving credit facility. The notes will be structurally subordinated to all liabilities of our subsidiaries.

The notes will not be listed on any securities exchange. Currently there is no public market for the notes.

Our common stock is listed on the New York Stock Exchange under the symbol “X.” The last reported sale price of our common stock on the New York Stock Exchange on March 20, 2013 was $19.45 per share.

Concurrently with this offering of notes, under a separate prospectus supplement, we are offering $275,000,000 aggregate principal amount of 6.875% Senior Notes due 2021. Neither offering will be contingent on completion of the other.

Investing in the notes involves risks that are described in the “Risk factors” section beginning on page S-7 of this prospectus supplement and the “Risk Factors” section beginning on page 31 of our annual report on Form 10-K for the fiscal year ended December 31, 2012, which is incorporated by reference into this prospectus supplement and the accompanying prospectus.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

We have granted the underwriters an option to purchase, within the 30-day period from the date of this prospectus supplement, up to an additional $41,250,000 aggregate principal amount of the notes.

The notes will be ready for delivery in book-entry form only through the facilities of The Depository Trust Company for the accounts of its participants, on or about March 26, 2013.

Joint book-running managers

The date of this prospectus supplement is March 20, 2013.

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Prospectus supplement

Prospectus

In making your investment decision, you should rely only on the information contained or incorporated by reference in this prospectus supplement and the accompanying prospectus. We have not, and the underwriters have not, authorized anyone to provide you with additional or different information. If anyone provides you with different or inconsistent information, you should not rely on it. We are not, and the underwriters are not, making an offer of these securities in any jurisdiction where the offer or sale is not permitted. You should not assume that the information contained in or incorporated by reference in this prospectus supplement or the accompanying prospectus is accurate as of any time subsequent to the date of such information.

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About this prospectus supplement

This document consists of two parts. The first part is the prospectus supplement, which describes the specific terms of this offering and certain other matters relating to ÁñÁ«ÊÓƵ. The second part, the accompanying prospectus, gives more general information about securities we may offer from time to time, some of which do not apply to this offering. Generally, when we refer to the prospectus, we are referring to both parts of this document combined. For information about our notes and our common stock, see “Description of notes” and “Description of common stock” in this prospectus supplement and “Description of the Debt Securities” and “Description of Capital Stock” in the accompanying prospectus. If the description in the prospectus supplement differs from the description in the accompanying prospectus, the description in the prospectus supplement supersedes the description in the accompanying prospectus. If the information in this prospectus supplement varies in any way from the information set forth in a document we have incorporated by reference, you should rely on the information in the more recent document.

Incorporation of certain information by reference

The Securities and Exchange Commission (SEC) allows us to “incorporate by reference” into this prospectus supplement the information in documents we file with it, which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is considered to be a part of this prospectus supplement, and later information that we file with the SEC will update and supersede this information. We incorporate by reference the documents listed below and any future filings we make with the SEC under Section 13(a), 13(c), 14, or 15(d) of the Securities Exchange Act of 1934 prior to the termination of the offering under this prospectus supplement (other than any documents or information deemed to have been furnished and not filed in accordance with the SEC rules). These documents contain important information about us. The SEC file number for these documents is 1-16811.

Any statement contained in a document incorporated by reference into this prospectus supplement will be deemed to be modified or superseded for purposes of this prospectus supplement to the extent that a statement contained herein or in any other subsequently filed document which is also incorporated by reference herein modifies or supersedes such statement. Any such statement so modified or superseded will not be deemed to constitute a part of this prospectus supplement except as so modified or superseded.

Forward-looking statements

We include “forward-looking” statements concerning trends, market forces, commitments, material events, and other contingencies potentially affecting our future performance in our annual and quarterly reports, press releases and other statements incorporated by reference into

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this prospectus supplement and the accompanying prospectus. These statements include, without limitation, statements regarding our general business strategies; financing decisions; projections of levels of revenues or production, income from operations, income from operations per ton, net income or earnings per share; levels of capital, environmental or maintenance expenditures; levels of employee benefits; the success or timing of completion of ongoing or anticipated capital or maintenance projects; levels of raw steel production capability; prices; production; shipments; labor and raw material costs; availability of raw materials; the acquisition, idling, shutdown or divestiture of assets or businesses; the effect of restructuring or reorganization of business components and cost reduction programs; the effect of steel industry consolidation; the effect of potential legal proceedings on our business and financial condition; the effects of actions of third parties, such as competitors or foreign, federal, state or local environmental or other regulatory authorities; the impact of international trade relief, import quotas, tariffs and other protectionist measures; and general economic conditions. These forward-looking statements are estimates based on currently available competitive, financial and economic data and our operating plans and involve risks, uncertainties and assumptions. As a result, these statements are inherently uncertain, and investors must recognize that events could turn out to be significantly different from our expectations. All subsequent written and oral forward-looking statements attributable to us, or persons acting on our behalf, are expressly qualified in their entirety by these cautionary statements. We do not undertake to update our forward-looking statements to reflect future events or circumstances, except as may be required by applicable law. Additional information regarding the risks and uncertainties that could impact our forward-looking statements is contained in our periodic filings with the SEC, including our Annual Report on Form 10-K for the year ended December 31, 2012.

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Risk factors

Before investing in the notes, you should carefully consider the risks set forth in Item 1A of our annual report on Form 10-K for the year ended December 31, 2012, as well as the following risks. These risks are not the only ones facing us. Additional risks not presently known to us or that we currently deem immaterial may also impair our business operations or the value of the notes.

Risks related to an investment in the notes and our common stock

The notes will be effectively junior to the Credit Facility and any other secured indebtedness that we may issue in the future.

The notes are unsecured. Holders of our secured debt may foreclose on the assets securing such debt, reducing the cash flow from the foreclosed property available for payment of unsecured debt, including the notes. We have granted the lenders under our $875 million revolving Credit Facility a first lien on the majority of our domestic inventories and certain accounts receivable. Holders of our secured debt also would have priority over unsecured creditors in the event of our bankruptcy, liquidation or similar proceeding to the extent of the value of the collateral securing such indebtedness. As a result, the notes will be effectively junior to the Credit Facility, secured obligations under capital leases and any secured debt that we may issue in the future to the extent of the value of the collateral securing such indebtedness.

The notes are obligations exclusively of U. S. Steel and not of our subsidiaries, and payment to holders of the notes will be structurally subordinated to the claims of our subsidiaries’ creditors.

The notes are not guaranteed by any of our subsidiaries. As a result, indebtedness or guarantees of indebtedness, and other liabilities of each of our subsidiaries, will effectively rank senior to the indebtedness represented by the notes, to the extent of such subsidiary’s assets. As of December 31, 2012, our subsidiaries had an aggregate of approximately $151 million of indebtedness outstanding, consisting of C$150 million due to the Province of Ontario. In addition, the indenture governing the notes does not restrict the future incurrence of liabilities or issuance of preferred stock, including unsecured indebtedness or guarantees of indebtedness, by our subsidiaries.

The notes do not contain restrictive financial covenants and we may incur substantially more debt or take other actions which may affect our ability to satisfy our obligations under the notes.

Other than as described under “Description of notes—Covenants—Limitation on liens” and “—Limitation on sale and leaseback transactions,” the indenture governing the notes does not contain any financial or operating covenants or restrictions on the incurrence of indebtedness (including secured debt), the payments of dividends or the issuance or repurchase of securities by us or any of our subsidiaries. In addition, the limited covenants applicable to the notes do not require us to achieve or maintain any minimum financial results relating to our financial position or results of operations.

Our ability to recapitalize, incur additional debt and take a number of other actions that are not limited by the terms of the notes could have the effect of diminishing our ability to make payments on the notes when due, and require us to dedicate a substantial portion of our cash flow from operations to payments on our indebtedness, which would reduce the availability of cash flow to fund our operations, working capital and capital expenditures.

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We may not have the ability to raise the funds necessary to settle conversion of the notes or to purchase the notes upon a fundamental change, and our future debt may contain limitations on our ability to pay cash upon conversion or repurchase of the notes.

Holders of the notes will have the right to require us to repurchase the notes upon the occurrence of a fundamental change at 100% of their principal amount plus accrued and unpaid interest, as described under “Description of notes—Fundamental change permits holders to require us to purchase notes.” In addition, upon conversion of the notes, unless we elect to deliver solely shares of our common stock to settle such conversion (other than cash in lieu of any fractional share), we will be required to make cash payments in respect of the notes being converted as described under “Description of notes—Conversion rights—Settlement upon conversion.” However, we may not have enough available cash or be able to obtain financing at the time we are required to make repurchases of tendered notes or pay or pay and deliver our conversion obligation with respect to notes being converted. In addition, our ability to repurchase the notes may be limited by law, by regulatory authority or by the agreements governing our future indebtedness. Our failure to repurchase tendered notes at a time when the repurchase is required by the indenture or to pay any cash payable upon future conversions of the notes as required by the indenture would constitute a default under the indenture. A default under the indenture or the fundamental change itself could also lead to a default or require a prepayment under, or result in the acceleration of the maturity or repurchase of, our existing or future indebtedness. If the repayment of the related indebtedness were to be accelerated after any applicable notice or grace periods, we may not have sufficient funds to repay the indebtedness and repurchase the notes.

Recent regulatory actions may adversely affect the trading price and liquidity of the notes.

Investors in, and potential purchasers of, the notes who employ, or seek to employ, a convertible arbitrage strategy with respect to the notes may be adversely impacted by regulatory developments that may limit or restrict such a strategy. The SEC and other regulatory and self-regulatory authorities have implemented various rules and may adopt additional rules in the future that restrict and otherwise regulate short selling and over-the-counter swaps and security-based swaps, which restrictions and regulations may adversely affect the ability of investors in, or potential purchasers of, the notes to conduct a convertible arbitrage strategy with respect to the notes. This could, in turn, adversely affect the trading price and liquidity of the notes.

The conditional conversion feature of the notes could result in your receiving less than the value of our common stock into which the notes would otherwise be convertible.

Prior to the close of business on the business day immediately preceding October 1, 2018, you may convert your notes only if specified conditions are met. If the specific conditions for conversion are not met, you will not be able to convert your notes, and you may not be able to receive the value of the cash, common stock or a combination of cash and common stock, as applicable, into which the notes would otherwise be convertible. Therefore, you may not be able to realize the appreciation, if any, in the value of our common stock after the issuance of the notes in the offering and prior to such date. In addition, the inability to freely convert may also adversely affect the trading price of the notes and your ability to sell the notes.

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Upon conversion of the notes, you may receive less valuable consideration than expected because the value of our common stock may decline after you exercise your conversion right but before we settle our conversion obligation.

Under the notes, a converting holder will be exposed to fluctuations in the value of our common stock during the period from the date such holder surrenders notes for conversion until the date we settle our conversion obligation.

Upon conversion of the notes, we have the option to pay or deliver, as the case may be, cash, shares of our common stock, or a combination of cash and shares of our common stock. If we elect to satisfy our conversion obligation in cash or a combination of cash and shares of our common stock, the amount of consideration that you will receive upon conversion of your notes will be determined by reference to the volume weighted average prices of our common stock for each VWAP trading day in a 20 VWAP trading day observation period. Although the number of shares (if any) that you receive upon conversion of your notes with respect to any VWAP trading day during the observation period will be determined based on the volume weighted average price of our common stock on such VWAP trading day, we will not deliver such shares until the third business day following the end of the relevant observation period. Accordingly, if the price of our common stock decreases during this period, the amount and/or value of consideration you receive will be adversely affected.

The adjustment to the conversion rate for notes converted in connection with a make-whole fundamental change or redemption may not adequately compensate you for any lost value of your notes as a result of such transaction.

If a make-whole fundamental change occurs prior to maturity or we elect to redeem the notes, under certain circumstances, we will increase the conversion rate by a number of additional shares of our common stock for notes converted in connection with such make-whole fundamental change or redemption. The increase in the conversion rate will be determined based on the date on which the specified corporate transaction becomes effective or the date upon which we give a notice of redemption and the price paid (or deemed paid) per share of our common stock in such transaction, as described below under “Description of notes—Conversion rights—Adjustment to conversion rate upon conversion upon a make-whole fundamental change or a notice of redemption.” The adjustment to the conversion rate for notes converted in connection with a make-whole fundamental change or redemption may not adequately compensate you for any lost value of your notes as a result of such transaction. In addition, if the price of our common stock in the transaction is greater than $80.00 per share or less than $19.45 per share (in each case, subject to adjustment), no adjustment will be made to the conversion rate. Moreover, in no event will the total number of shares of common stock issuable upon conversion as a result of this adjustment exceed 51.4138 shares per $1,000 principal amount of notes, subject to adjustments in the same manner as the conversion rate as set forth under “Description of notes—Conversion rights—Conversion rate adjustments.”

Our obligation to increase the conversion rate upon the occurrence of a make-whole fundamental change or redemption could be considered a penalty, in which case the enforceability thereof would be subject to general principles of reasonableness of economic remedies.

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The conversion rate of the notes may not be adjusted for all dilutive events.

The conversion rate of the notes is subject to adjustment for certain events, including, but not limited to, the issuance of stock dividends on our common stock, the issuance of certain rights or warrants, subdivisions, combinations, distributions of capital stock, indebtedness, or assets, cash dividends and certain issuer tender or exchange offers as described under “Description of notes—Conversion rights—Conversion rate adjustments.” However, the conversion rate will not be adjusted for other events, such as a third-party tender or exchange offer or an issuance of common stock for cash or in an acquisition, that may adversely affect the trading price of the notes or the common stock. An event that adversely affects the value of the notes may occur, and that event may not result in an adjustment to the conversion rate.

Some significant restructuring transactions may not constitute a fundamental change, in which case we would not be obligated to offer to repurchase the notes.

Upon the occurrence of a fundamental change, you have the right to require us to repurchase your notes. However, the fundamental change provisions will not afford protection to holders of notes in the event of other transactions that could adversely affect the notes. For example, transactions such as leveraged recapitalizations, refinancings, restructurings, or acquisitions initiated by us may not constitute a fundamental change requiring us to repurchase the notes. In the event of any such transaction, the holders would not have the right to require us to repurchase the notes, even though each of these transactions could increase the amount of our indebtedness, or otherwise adversely affect our capital structure or any credit ratings, thereby adversely affecting the holders of notes. In addition, not all transactions that require us to offer to repurchase our outstanding senior notes or repay amounts outstanding under our Credit Facility will require us to offer to repurchase the notes offered hereby.

There is no public market for the notes, which could limit their market price or your ability to sell them.

The notes are a new issue of securities for which there currently is no trading market. As a result, a market may not develop for the notes and you may not be able to sell your notes. Any notes that are traded after their initial issuance may trade at a discount from their initial offering price. Future trading prices of the notes will depend on many factors, including prevailing interest rates, the market for similar securities, general economic conditions and our financial condition, performance and prospects. Accordingly, you may be required to bear the financial risk of an investment in the notes for an indefinite period of time. We do not intend to apply for listing or quotation of the notes on any securities exchange or automated quotation system. While the underwriters may make a market in the notes they are not required to do so and consequently any market making with respect to the notes may be discontinued at any time without notice. Even if the underwriters make a market in the notes the liquidity of such a market may be limited. See “Underwriting.”

The accounting method for convertible debt securities that may be settled in cash, such as the notes, could have a material effect on our reported financial results.

In 2008, the Financial Accounting Standards Board, which we refer to as FASB, issued FASB Staff Position No. APB 14-1, Accounting for Convertible Debt Instruments That May Be Settled in Cash Upon Conversion (Including Partial Cash Settlement), which has subsequently been codified as Accounting Standards Codification 470-20, Debt with Conversion and Other Options, which we refer to as ASC 470-20. Under ASC 470-20, an entity must separately account for the liability and equity components of the convertible debt instruments (such as the notes) that may be settled

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entirely or partially in cash upon conversion in a manner that reflects the issuer’s economic interest cost. The effect of ASC 470-20 on the accounting for the notes is that the equity component is required to be included in the additional paid-in capital section of stockholders’ equity on our consolidated balance sheet, and the value of the equity component would be treated as original issue discount for purposes of accounting for the debt component of the notes. As a result, we will be required to record a greater amount of non-cash interest expense in current periods presented as a result of the amortization of the discounted carrying value of the notes to their face amount over the term of the notes. We will report lower net income in our financial results because ASC 470-20 will require interest to include both the current period’s amortization of the debt discount and the instrument’s coupon interest, which could adversely affect our reported or future financial results, the trading price of our common stock and the trading price of the notes.

In addition, convertible debt instruments (such as the notes) that may be settled entirely or partly in cash are, where the issuer has the intent and policy to settle such instruments partly in a cash amount equal to the principal amount, currently accounted for utilizing the treasury stock method, the effect of which is that the shares that would be issuable upon conversion of the notes are not included in the calculation of diluted earnings per share except to the extent that the conversion value of the notes exceeds their principal amount. Under the treasury stock method, for diluted earnings per share purposes, the transaction is accounted for as if the number of shares of common stock that would be necessary to settle such excess, if we elected to settle such excess in shares, are issued. We cannot be sure that the accounting standards in the future will continue to permit the use of the treasury stock method. If we are unable to use the treasury stock method in accounting for the shares issuable upon conversion of the notes, then our diluted earnings per share would be adversely affected.

Fluctuations in the price of our common stock may impact the price of the notes and make them more difficult to resell.

The market price of our common stock has been and may continue to be subject to significant fluctuations due not only to general stock market conditions but also to a change in sentiment in the market regarding our operations, business prospects, liquidity or this offering. In addition to the risk factors discussed in our Annual Report on Form 10-K for the year ended December 31, 2012, the price volatility of our common stock may be affected by:

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The stock markets in general have experienced extreme volatility that has at times been unrelated to the operating performance of particular companies. These broad market fluctuations may adversely affect the trading price of our common stock, make it difficult to predict the market price of our common stock in the future and cause the value of your investment to decline.

Because the notes are convertible into shares of our common stock, volatility or depressed prices of our common stock could have a similar effect on the trading price of the notes. Holders who receive common stock upon conversion of the notes will also be subject to the risk of volatility and depressed prices of our common stock.

Changes in our credit ratings or the debt markets may adversely impact the market price of the notes or our common stock.

The price for the notes will also depend on a number of other factors, including:

The condition of the financial markets and prevailing interest rates have fluctuated in the past and are likely to fluctuate in the future. Such fluctuations could have an adverse effect on the price of the notes. In addition, credit rating agencies continually review their ratings for the companies that they follow, including us, and the industries in which we operate as a whole. If in the future one or more rating agencies were to reduce or withdraw their rating, or place the notes on a “watch list,” the market price of the notes and our common stock may be adversely affected.

There may be future sales or other dilution of our equity, which may adversely affect the market price of our common stock and the value of the notes.

Except as described under “Underwriting,” we are not restricted from issuing additional common stock, including securities that are convertible into or exchangeable for, or that represent the right to receive, common stock. The issuance of additional shares of our common stock upon conversion of the notes or other issuances of our common stock or convertible securities, including outstanding options and warrants, or otherwise will dilute the ownership interest of our common stockholders.

Sales of a substantial number of shares of our common stock or other equity-related securities could depress the market price of the notes, our common stock, or both, and impair our ability to raise capital through the sale of additional equity securities. We cannot predict the effect that future sales of our common stock or other equity-related securities would have on the market price of our common stock or the value of the notes. The price of our common stock could be affected by possible sales of our common stock by investors who view the notes as a more attractive means of equity participation in our company and by hedging or arbitrage trading activity that we expect to develop involving our common stock as a result of this offering. The hedging or arbitrage could, in turn, affect the market price of the notes.

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Holders of notes will not be entitled to any rights with respect to our common stock, but will be subject to all changes made with respect to them to the extent our conversion obligation includes shares of our common stock.

Holders of notes will not be entitled to any rights with respect to our common stock (including, without limitation, voting rights and rights to receive any dividends or other distributions on our common stock), but holders of notes will be subject to all changes affecting our common stock. For example, if an amendment is proposed to our restated certificate of incorporation or amended and restated by-laws requiring shareholder approval, and the record date for determining the shareholders of record entitled to vote on the amendment occurs prior to date a holder is deemed to be the record owner of the shares of our common stock due upon conversion, such holder will not be entitled to vote on the amendment, although such holder will nevertheless be subject to any changes in the powers, preferences or special rights of our common stock.

Provisions of the notes could discourage an acquisition of us by a third party.

Certain provisions of the notes could make it more difficult or expensive for a third party to acquire us. Upon the occurrence of certain transactions constituting a fundamental change, holders of the notes will have the right, at their option, to require us to repurchase all of their notes or any portion of the principal amount of such notes in integral multiples of $1,000. We may also be required to issue additional shares upon conversion in the event of certain fundamental change transactions. These provisions could deter unsolicited takeovers, including transactions in which stockholders might otherwise receive a premium for their shares over the then current market price or could limit the price that some investors might be willing to pay in the future for shares of our common stock.

If we increase the cash dividend on our common stock, or otherwise adjust the conversion rate, a holder may be deemed to have received a taxable dividend without the receipt of any cash.

If we increase the cash dividend on our common stock, an adjustment to the conversion rate may result, and a holder may be deemed to have received a taxable dividend subject to United States federal income tax without the receipt of any cash. A holder may also be deemed to have received a taxable dividend upon certain other adjustments to the conversion rate, including upon a make-whole fundamental change or notice of redemption. If a holder is a non-United States holder (as defined in “Certain United States federal income and estate tax considerations”), such deemed dividend may be subject to United States federal withholding tax at a 30% rate or such lower rate as may be specified by an applicable treaty. See “Certain United States federal income and estate tax considerations.”

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Ratio of earnings to fixed charges

The following table sets forth the ratio of our earnings to fixed charges for the periods indicated:

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Common stock price range and dividends

Our common stock is listed on the New York Stock Exchange under the symbol “X.” The following table sets forth, for the periods indicated, the high and low sales prices per share of our common stock as reported on the NYSE and the dividends declared per share of our common stock.

The last reported sale price of our common stock on the New York Stock Exchange on March 20, 2013 was $19.45 per share. As of March 15, 2013, there were 144,283,311 shares of our common stock outstanding held by approximately 17,542 registered holders.

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Use of proceeds

The net proceeds from the sale of the notes in this offering are estimated to be approximately $266,767,500 (or approximately $306,863,125 if the underwriters exercise in full their option to purchase additional notes), after deducting underwriting discounts and our estimated expenses. We intend to use the net proceeds from this offering, together with the net proceeds from the concurrent Senior Notes Offering, for repurchases or repayment of indebtedness, focusing on near-term maturities, and any remaining proceeds for general corporate purposes.

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Capitalization

The following table sets forth our cash and cash equivalents and our capitalization as of December 31, 2012:

The “as adjusted” and “as further adjusted” columns reflect the net proceeds of this offering and the concurrent Senior Notes Offering, as applicable, in cash and cash equivalents. We intend to use the net proceeds of this offering and the concurrent Senior Notes Offering to repurchase or repay indebtedness, focusing on near-term maturities (and any remaining proceeds for general corporate purposes). After giving effect to the repurchase and repayment of indebtedness, we expect the amount of our total debt (excluding the debt discount to be recognized with respect to the notes offered hereby) to remain approximately the same.

You should read the following table in conjunction with the section entitled “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and our financial statements and notes included in our most recent Annual Report on Form 10-K, which is incorporated by reference in this document, and with the sections entitled “Description of notes” and “Description of common stock” in this prospectus supplement and the “Description of the Debt Securities” and “Description of Capital Stock” in the accompanying prospectus.

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Description of notes

The following description of the particular terms of the notes offered by this prospectus supplement supplements the description of the general terms and provisions of the debt securities set forth in the accompanying prospectus following the caption “Description of the Debt Securities.” This description of notes supplements, and to the extent it is inconsistent, replaces the description of the general provisions of the notes and the base indenture (as defined below) set forth in the accompanying prospectus.

The notes will be issued under an indenture dated May 21, 2007 (as supplemented to date, the “base indenture”), as supplemented by a Seventh Supplemental Indenture to be executed as of the closing of this offering (together with the base indenture, the “indenture”), between us and The Bank of New York Mellon (formerly The Bank of New York), as trustee. The indenture is subject to and is governed by the Trust Indenture Act of 1939, as amended (the “Trust Indenture Act”). We have filed the base indenture as an exhibit to the registration statement of which the accompanying prospectus forms a part. The following description summarizes selected provisions of the indenture and the notes. It does not restate the indenture or the terms of the notes in their entirety. We urge you to read the forms of the indenture and the notes because the indenture and the notes fully define the rights of noteholders.

For purposes of this description, references to:

Unless the context otherwise requires, all references to interest in this prospectus supplement are deemed to include additional interest, if any, payable at our election as the sole remedy relating to the failure to comply with our reporting obligations as described under “—Events of default”.

General

The notes will:

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Subject to satisfaction of certain conditions and during the periods described below, the notes may be converted at an initial conversion rate of 39.5491 shares of common stock per $1,000 principal amount of notes (equivalent to an initial conversion price of approximately $25.29 per share of common stock). The conversion rate is subject to adjustment if certain events occur.

We will settle conversions of notes by paying or delivering, as the case may be, cash, shares of our common stock or a combination of cash and shares of our common stock, at our election, as described under “—Conversion rights—Settlement upon conversion”. You will not receive any separate cash payment for interest, if any, accrued and unpaid to the conversion date except under the limited circumstances described below.

Except as described under “—Covenants—Limitation on liens” and “—Covenants —Limitation on sale and leaseback transactions,” neither we nor any of our subsidiaries will be restricted by the indenture from any of the following:

In addition, we will not be required to maintain any financial ratios or specified levels of net worth or liquidity or to repurchase or redeem or otherwise modify the terms of any of the notes upon a change of control or other events involving us or any of our subsidiaries which may adversely affect the creditworthiness or value of the notes, except to the limited extent described following the captions “—Conversion rights—Adjustment to conversion rate upon conversion upon a make-whole fundamental change or notice of redemption”, “—Fundamental change permits holders to require us to purchase notes” and “—Merger, consolidation or sale of assets.” Among other things, the indenture will not contain covenants designed to afford holders of the notes any protections in the event of a highly leveraged or other transaction involving us that may adversely affect holders of the notes, except to the limited extent described following the caption “—Fundamental change permits holders to require us to purchase notes.”

We use the term “note” in this prospectus supplement, unless the context otherwise requires, to refer to each $1,000 principal amount of notes. Subject to “—Recapitalizations, reclassifications and changes of our common stock” below, we use the term “common stock” in this prospectus supplement to refer to our common stock, $1 par value per share.

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We do not intend to list the notes on any securities exchange or any automated dealer quotation system.

The notes will not be guaranteed by any of our subsidiaries. No sinking fund is provided for the notes, and the notes will not be subject to defeasance.

Additional notes

We may, without the consent of the holders, issue additional notes under the indenture in the future with the same terms as the notes offered hereby (except for any differences in issue price) in an unlimited aggregate principal amount; provided that if any such additional notes are not fungible with the notes initially offered hereby for U.S. federal income tax purposes, such additional notes will have a separate CUSIP number.

Purchase and cancellation

We will cause all notes surrendered for payment, repurchase (including as described below, but excluding notes repurchased pursuant to cash-settled swaps or other derivatives), registration of transfer or exchange or conversion, if surrendered to any person other than the trustee (including any of our agents, subsidiaries or affiliates), to be delivered to the trustee for cancellation, and they will no longer be considered “outstanding” under the indenture. All notes delivered to the trustee shall be cancelled promptly by the trustee. No notes shall be authenticated in exchange for any notes cancelled as provided in the indenture.

We may, to the extent permitted by law, and directly or indirectly (regardless of whether such notes are surrendered to us), repurchase notes in the open market or otherwise, whether by us or our subsidiaries or through a private or public tender or exchange offer or through counterparties to private agreements, including cash-settled swaps or other derivatives.

Payments on the notes; Paying agent and registrar; transfer and exchange

We will pay the principal of, and interest on, notes in global form registered in the name of or held by The Depository Trust Company (“DTC”) or its nominee in immediately available funds to DTC or its nominee, as the case may be, as the registered holder of such global note.

We will pay the principal of any certificated notes at the office or agency designated by us for that purpose. We have initially designated the trustee as our paying agent and registrar and its corporate trust office as a place where notes may be presented for payment or for registration of transfer. We may, however, change the paying agent or registrar without prior notice to the holders of the notes, and we may act as paying agent or registrar. Interest on certificated notes will be payable (i) to holders holding certificated notes having an aggregate principal amount of $5,000,000 or less, by check mailed to the holders of these notes and (ii) to holders holding certificated notes having an aggregate principal amount of more than $5,000,000, either by check mailed to each holder or, upon application by such a holder to the registrar not later than the relevant regular record date, by wire transfer in immediately available funds to that holder’s account within the United States, which application shall remain in effect until the holder notifies, in writing, the registrar to the contrary.

A holder of notes may transfer or exchange notes as described under “Description of the Debt Securities—Book-Entry Securities” in the accompanying prospectus. However, we are not required to transfer or exchange any note surrendered for conversion, redemption or required purchase.

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The registered holder of a note will be treated as its owner for all purposes.

Interest

The notes will bear cash interest at a rate of 2.75% per year until maturity. Interest on the notes will accrue from their first date of initial issuance or from the most recent date on which interest has been paid or duly provided for. Interest will be payable semiannually in arrears on April 1 and October 1 of each year, beginning on October 1, 2013.

Interest will be paid to the person in whose name a note is registered at the close of business on March 15 or September 15 (whether or not a business day), as the case may be, immediately preceding the relevant interest payment date (each, a “regular record date”). Interest on the notes will be computed on the basis of a 360-day year composed of twelve 30-day months.

If any interest payment date, the maturity date, a redemption date or any earlier required purchase date upon a fundamental change of a note falls on a day that is not a business day, the required payment will be made on the next succeeding business day and no interest on such payment will accrue in respect of the delay.

Ranking

The notes will be our senior and unsecured indebtedness and will rank equally with all of our other existing and future senior and unsecured indebtedness. The notes will effectively rank junior to any of our existing and future secured indebtedness to the extent of the assets securing such indebtedness, and will be structurally subordinated to any indebtedness and other liabilities of our subsidiaries. Indebtedness of our subsidiaries and obligations and liabilities of our subsidiaries are structurally senior to the notes since, in the event of our bankruptcy, liquidation, dissolution, reorganization or other winding up, the assets of our subsidiaries will be available to pay the notes only after the subsidiaries’ indebtedness and obligations and liabilities are paid in full. Because we generally stand as an equity holder, rather than a creditor, of our subsidiaries, creditors of those subsidiaries will have their debt satisfied out of the subsidiaries’ assets before our creditors, including the noteholders.

As of December 31, 2012, we had an aggregate of approximately $3,818 million of senior indebtedness outstanding (consisting of approximately $3,163 million of senior notes, $549 million of obligations relating to environmental revenue bonds, $70 million relating to recovery zone facility bonds, and $36 million of obligations under capital leases and other debt). In addition, as of December 31, 2012, we had no outstanding borrowings based on receivables sold to third-party conduits under our Receivables Purchase Agreement.

As of December 31, 2012, our subsidiaries had an aggregate amount of indebtedness outstanding of approximately $151 million (consisting of C$150 million (approximately $151 million using exchange rates as of December 31, 2012) outstanding under the Province note), which would be structurally senior to the notes offered hereby.

Conversion rights

General

Prior to the close of business on the business day immediately preceding October 1, 2018, the notes will be convertible only upon satisfaction of one or more of the conditions described under

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the headings “—Conversion upon satisfaction of sale price condition”, “—Conversion upon satisfaction of trading price condition”, “—Conversion upon notice of redemption” and “—Conversion upon specified corporate events”. On or after October 1, 2018 until the close of business on the second scheduled trading day immediately preceding the maturity date, holders may convert their notes at the conversion rate at any time.

The conversion rate will initially be 39.5491 shares of common stock per $1,000 principal amount of notes (equivalent to an initial conversion price of approximately $25.29 per share of common stock). The conversion rate and the corresponding conversion price in effect at any given time are referred to as the “applicable conversion rate” and the “applicable conversion price”, respectively, and will be subject to adjustment as described below. The applicable conversion price at any given time will be computed by dividing $1,000 by the applicable conversion rate at such time. A holder may convert fewer than all of such holder’s notes so long as the notes converted are an integral multiple of $1,000 principal amount. The trustee will initially act as the conversion agent.

Upon conversion of a note, we will satisfy our conversion obligation by paying or delivering, as the case may be, cash, shares of our common stock or a combination of cash and shares of our common stock, at our election, all as set forth below under “—Settlement upon conversion.” If we satisfy our conversion obligation solely in cash or through payment and delivery, as the case may be, of a combination of cash and shares of our common stock, the amount of cash and shares of common stock, if any, due upon conversion will be based on a daily conversion value (as defined below) calculated on a proportionate basis for each VWAP trading day in a 20 VWAP trading day observation period (as defined below under “—Settlement upon conversion”).

If a holder of notes has submitted notes for purchase upon a fundamental change, the holder may convert those notes only if that holder first withdraws its purchase notice.

Upon conversion, you will not receive any separate cash payment for accrued and unpaid interest, if any, except as described below. Except in the circumstances described below under “—Conversion upon notice of redemption”, our payment and delivery, as the case may be, to you of the cash, shares of our common stock or a combination thereof, as the case may be, into which a note is convertible will be deemed to satisfy in full our obligation to pay:

As a result, accrued and unpaid interest, if any, to, but not including, the relevant conversion date will be deemed to be paid in full rather than cancelled, extinguished or forfeited (except in the circumstances described under “—Conversion upon notice of redemption”).

Notwithstanding the immediately preceding paragraph, if notes are converted after the close of business on a regular record date for the payment of interest, but prior to the open of business on the immediately following interest payment date, holders of such notes at the close of business on such regular record date will receive the full amount of interest payable on such notes on the corresponding interest payment date notwithstanding the conversion. Notes surrendered for conversion during the period from the close of business on any regular record date to the open of business on the immediately following interest payment date must be accompanied by funds equal to the amount of interest payable on the notes so converted

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(regardless of whether the converting holder was the holder of record on the corresponding regular record date); provided that no such payment need be made:

Therefore, for the avoidance of doubt, all holders on the regular record date immediately preceding the maturity date will receive and retain the full interest payment due on the maturity date regardless of whether their notes are converted following such record date.

We will not issue fractional shares of our common stock upon conversion of notes. Instead, we will pay cash in lieu of any fractional share as described under “—Settlement upon conversion”.

If a holder converts notes, we will pay any documentary, stamp or similar issue or transfer tax due on any issuance of any shares of our common stock upon the conversion, unless the tax is due because the holder requests such shares to be issued in a name other than the holder’s name, in which case the holder will pay that tax.

Holders may surrender their notes for conversion under the following circumstances:

Conversion upon satisfaction of sale price condition

Prior to the close of business on the business day immediately preceding October 1, 2018, a holder may surrender all or a portion of its notes for conversion during any calendar quarter commencing after the calendar quarter ending on June 30, 2013 (and only during such calendar quarter), if the last reported sale price of the common stock for at least 20 trading days (whether or not consecutive) during the period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter is greater than or equal to 130% of the conversion price on each applicable trading day.

The “last reported sale price” of our common stock on any date means the closing sale price per share (or if no closing sale price is reported, the average of the bid and ask prices or, if more than one in either case, the average of the average bid and the average ask prices) on that date as reported in composite transactions for the relevant stock exchange (as defined below). If our common stock is not listed, quoted or traded on any U.S. securities exchange or any other market, the “last reported sale price” will be the average of the mid-point of the last bid and ask prices for our common stock on the relevant date from each of at least three nationally recognized independent investment banking firms selected by us for this purpose.

“Trading day” means a day on which:

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If our common stock (or such other security) is not listed, quoted or traded on any U.S. securities exchange or any other market, “trading day” means a “business day”.

“Relevant stock exchange” means The New York Stock Exchange or, if our common stock (or other security for which a closing sale price must be determined) is not then listed on The New York Stock Exchange, the principal other U.S. national or regional securities exchange on which our common stock (or such other security) is then listed or, if our common stock (or such other security) is not then listed on a U.S. national or regional securities exchange, the over-the-counter market, as reported by OTC Markets Group Inc. or similar organization or, if our common stock is not then quoted by the OTC Markets Group Inc. or similar organization, the principal other market on which our common stock (or such other security) is then traded.

Conversion upon satisfaction of trading price condition

Prior to the close of business on the business day immediately preceding October 1, 2018, a holder of notes may surrender all or a portion of its notes for conversion during the five business day period after any five consecutive trading day period (the “measurement period”) in which the “trading price” per $1,000 principal amount of notes, as determined following a request by a holder of notes in accordance with the procedures described below, for each trading day of the measurement period was less than 98% of the product of the last reported sale price of our common stock and the conversion rate on each such trading day, subject to compliance with the procedures and conditions described below concerning the bid solicitation agent’s obligation to make a trading price determination.

The “trading price” of the notes on any date of determination means the average of the secondary market bid quotations obtained by the bid solicitation agent for $5,000,000 principal amount of notes at approximately 3:30 p.m., New York City time, on such determination date from three independent nationally recognized securities dealers we select; provided that if three such bids cannot reasonably be obtained by the bid solicitation agent but two such bids are obtained, then the average of the two bids shall be used, and if only one such bid can reasonably be obtained by the bid solicitation agent, that one bid shall be used. If the bid solicitation agent cannot reasonably obtain at least one bid for $5,000,000 principal amount of notes from a nationally recognized securities dealer, then the trading price per $1,000 principal amount of notes will be deemed to be less than 98% of the product of the last reported sale price of our common stock and the conversion rate.

The bid solicitation agent (if other than us) shall have no obligation to determine the trading price per $1,000 principal amount of notes unless we have requested such determination and we shall have no obligation to make such request (or, if we are acting as bid solicitation agent, we shall have no obligation to determine the trading price) unless a holder of a note provides us with reasonable evidence that the trading price per $1,000 principal amount of notes would be less than 98% of the product of the last reported sale price of our common stock and the conversion rate. At such time, we shall instruct the bid solicitation agent to (or, if we are acting as bid solicitation agent, we shall) determine the trading price per $1,000 principal amount of notes beginning on the next trading day and on each successive trading day until the trading price per $1,000 principal amount of notes is greater than or equal to 98% of the product of the last reported sale price of our common stock and the conversion rate. If the trading price condition has been met on any trading day, we will so notify the holders, the trustee and the conversion agent (if other than the trustee) on such trading day. If, at any time after the trading

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price condition has been met, the trading price per $1,000 principal amount of notes is greater than or equal to 98% of the product of the last reported sale price of our common stock and the conversion rate for such date, we will promptly so notify the holders, the trustee and the conversion agent (if other than the trustee). If we do not, when we are required to, instruct the bid solicitation agent to (or, if we are acting as bid solicitation agent, we do not) obtain bids, or if we give such instruction to the bid solicitation agent and the bid solicitation agent fails to make such determination, then, in either case, the trading price per $1,000 principal amount of notes will be deemed to be less than 98% of the product of the last reported sale price of our common stock and the conversion rate on each trading day of such failure.

We will initially act as the bid solicitation agent.

Conversion upon notice of redemption

If we call any or all of the notes for redemption, holders of the notes will have the right to convert all or a portion of their notes called for redemption at any time prior to the close of business on the business day immediately preceding the redemption date, after which time holders will no longer have the right to convert their notes on account of our delivery of notice of such redemption, unless we default in the payment of the redemption price. If a holder elects to convert its notes in connection with our redemption notice, we will:

Conversion upon specified corporate events

Certain distributions

If, prior to the close of business on the business day immediately preceding October 1, 2018, we elect to:

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then, in either case, we must notify the holders of the notes at least 30 scheduled trading days prior to the ex-dividend date (as defined below) for such issuance or distribution. Once we have given such notice, holders may surrender all or a portion of their notes for conversion at any time until the earlier of (x) the close of business on the business day immediately preceding the ex-dividend date for such issuance or distribution and (y) our declaration that such issuance or distribution will not take place, even if the notes are not otherwise convertible at such time.

Certain corporate events

Prior to the close of business on the business day immediately preceding October 1, 2018, if:

the notes may be surrendered for conversion at any time from or after the date that is 30 scheduled trading days prior to the anticipated effective date of the transaction (or, if later, the business day after we give notice of such transaction) until 35 trading days after the actual effective date of such transaction or, if such transaction also constitutes a fundamental change, until the related fundamental change purchase date.

If a holder has already delivered a purchase notice as described under “—Fundamental change permits holders to require us to purchase notes” with respect to a note, the holder may not surrender that note for conversion until the holder has withdrawn the purchase notice in accordance with the relevant provisions of the indenture. If a holder submits its notes for required purchase, the holder’s right to withdraw the purchase notice and convert the notes that are subject to required purchase will terminate at the close of business on the business day immediately preceding the relevant fundamental change purchase date.

We will notify holders as promptly as practicable following the date we publicly announce such transaction; provided that we will deliver such notice, to the extent practicable, at least 30 scheduled trading days prior to the anticipated effective date of the transaction, and in no event later than the actual effective date.

Conversions on or after October 1, 2018

On or after October 1, 2018, a holder may convert all or a portion of its notes at any time prior to the close of business on the second scheduled trading day immediately preceding the maturity date.

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Conversion procedures

If you hold a beneficial interest in a global note, to convert you must comply with DTC’s procedures for converting a beneficial interest in a global note and, if required, pay funds equal to interest payable on the next interest payment date to which you are not entitled, as described under “—Conversion rights—General”.

If you hold a certificated note, to convert you must:

We will pay any documentary, stamp or similar issue or transfer tax on the issuance of any shares of our common stock upon conversion of the notes, unless the tax is due because the holder requests such shares to be issued in a name other than the holder’s name, in which case the holder will pay the tax.

We refer to the date you comply with the relevant procedures for conversion described above as the “conversion date”.

Settlement upon conversion

Upon conversion, we may choose to pay or deliver, as the case may be, either:

We refer to each of these settlement methods as a “settlement method”.

All conversions occurring on or after October 1, 2018 will be settled using the same relative proportion of cash and/or shares of our common stock as all other conversions occurring on or after October 1, 2018. If we elect a settlement method, we will inform holders through the conversion agent of the settlement method we have selected no later than October 1, 2018. If we do not timely elect a settlement method, we will no longer have the right to elect cash settlement or physical settlement and we will be deemed to have elected combination settlement in respect of our conversion obligation, as described below, and the specified dollar amount (as defined below) per $1,000 principal amount of notes will be equal to $1,000. If we elect combination settlement, but we do not timely notify the conversion agent of the specified dollar amount per $1,000 principal amount of notes, such specified dollar amount will be deemed to be $1,000.

Except for any conversions that occur on or after October 1, 2018, we will use the same settlement method (including the same relative proportion of cash and/or shares of our common stock) for all conversions occurring on the same conversion date, but we will not have any

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obligation to use the same settlement method with respect to conversions that occur on different conversion dates. That is, we may choose for notes converted on one conversion date to settle conversions in physical settlement, and choose for notes converted on another conversion date cash settlement or combination settlement. If we elect a settlement method, we will inform holders so converting through the conversion agent of the settlement method we have selected no later than the close of business on the second trading day immediately following the related conversion date. If we do not timely elect a settlement method, we will no longer have the right to elect cash settlement or physical settlement with respect to that conversion date, and we will be deemed to have elected combination settlement in respect of our conversion obligation, as described below, and the specified dollar amount (as defined below) per $1,000 principal amount of notes will be equal to $1,000. If we elect combination settlement, but we do not timely notify the conversion agent of the specified dollar amount per $1,000 principal amount of notes, such specified dollar amount will be deemed to be $1,000.

It is our current intent and policy to settle all conversions through combination settlement with a specified dollar amount of $1,000.

Settlement amounts will be computed as follows:

If more than one note is surrendered for conversion at any one time by the same holder, the conversion obligation with respect to such notes shall be computed on the basis of the aggregate principal amount of the notes surrendered.

The “daily settlement amount”, for each of the 20 consecutive VWAP trading days during the observation period, shall consist of:

The “daily conversion value” means, for each of the 20 consecutive VWAP trading days during the observation period, 1/20^th of the product of:

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The “daily VWAP” means, for each of the 20 consecutive VWAP trading days during the applicable observation period, the per share volume-weighted average price as displayed under the heading “Bloomberg VWAP” on Bloomberg page “X <equity> AQR” (or its equivalent successor if such page is not available) in respect of the period from the scheduled open of trading until the scheduled close of trading of the primary trading session on such VWAP trading day (or if such volume-weighted average price is unavailable, the market value of one share of our common stock on such VWAP trading day reasonably determined, using a volume-weighted average method, by a nationally recognized independent investment banking firm retained for this purpose by us). The “daily VWAP” will be determined without regard to afterhours trading or any other trading outside of the regular trading session trading hours.

The “observation period” with respect to any note surrendered for conversion means:

“VWAP trading day” means a day on which:

If our common stock is not listed or admitted for trading on any U.S. securities exchange or any other market, “VWAP trading day” means a “business day”.

“Scheduled trading day” means a day that is scheduled to be a trading day on the relevant stock exchange. If our common stock is not listed, quoted or traded on any U.S. securities exchange or any other market, “scheduled trading day” means a “business day”.

“Market disruption event” means:

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Except as described under “—Adjustment to conversion rate upon conversion upon a make-whole fundamental change or a notice of redemption” and “—Recapitalizations, reclassifications and changes of our common stock”, we will deliver the consideration due in respect of conversion on:

We will deliver cash in lieu of any fractional share of common stock issuable upon conversion based on:

Each conversion will be deemed to have been effected as to any notes surrendered for conversion on the conversion date; provided, however, that the person in whose name any shares of our common stock shall be issuable upon such conversion will be treated as the holder of record of such shares as of the close of business on the conversion date, in the case of physical settlement, or the last VWAP trading day of the relevant observation period, in the case of combination settlement.

Exchange in lieu of conversion

When a holder surrenders its notes for conversion, we may, at our election (an “exchange election”), direct the conversion agent to surrender, on or prior to the second trading day following the conversion date, such notes to a financial institution designated by us for exchange in lieu of conversion. In order to accept any notes surrendered for conversion, the designated institution must agree to timely deliver, in exchange for such notes, the shares of our common stock and/or cash due upon conversion as described above under “—Settlement upon conversion” (the “conversion consideration”). If we make an exchange election, we will, by the close of business on the second trading day following the relevant conversion date, notify the holder surrendering its notes for conversion that we have made the exchange election and we will notify the designated financial institution of the settlement method we have elected with respect to such conversion and the relevant deadline for delivery of the conversion consideration.

Any notes exchanged by the designated institution will remain outstanding. If the designated institution agrees to accept any notes for exchange but does not timely deliver the related conversion consideration, or if such designated financial institution does not accept the notes for exchange, we will deliver the relevant conversion consideration to the converting holder at the time and in the manner required under the indenture as if we had not made an exchange election.

Our designation of an institution to which the notes may be submitted for exchange does not require the institution to accept any notes.

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Conversion rate adjustments

The applicable conversion rate will be adjusted as described below, except that we will not make any adjustments to the conversion rate if holders of the notes participate (other than in the case of a share split or share combination), as a result of holding the notes, and contemporaneously with common stock holders, in any of the transactions described below as if such holders of the notes held a number of shares of our common stock equal to the applicable conversion rate, multiplied by the principal amount (expressed in thousands) of notes held by such holder, without having to convert their notes.

where,

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where,

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then the applicable conversion rate will be increased based on the following formula:

where,

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With respect to an adjustment pursuant to this clause (3) where there has been a payment of a dividend or other distribution on our common stock of shares of capital stock of any class or series, or similar equity interest, of or relating to a subsidiary or other business unit, that are, or, when issued, will be, listed or admitted for trading on a U.S. national securities exchange, which we refer to as a “spin—off”, the applicable conversion rate will be increased based on the following formula:

where,

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where,

where,

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where,

The increase to the applicable conversion rate under the preceding paragraph will be determined at the close of business on the 10th trading day immediately following, and including, the trading day next succeeding the date such tender or exchange offer expires, but will be given effect at the open of business on the trading day next succeeding the date such tender or exchange offer expires. Notwithstanding the foregoing, in respect of any conversion within the 10 trading days immediately following, and including, the trading day next succeeding the expiration date of any tender or exchange offer, references in the preceding paragraph with respect to 10 trading days shall be deemed replaced with such lesser number of trading days as have elapsed between the expiration date of such tender or exchange offer and the conversion date in determining the conversion rate. In addition, if the trading day next succeeding the expiration date is less than 10 trading days prior to, and including, the end of the observation period in respect of any conversion, references in the preceding paragraph to 10 trading days shall be deemed to be replaced, solely in respect of that conversion, with such lesser number of trading days as have elapsed from, and including, the trading day next succeeding the expiration date to, and including, the last trading day of such observation period. For the avoidance of doubt, no adjustment under this clause (5) will be made if such adjustment would result in a decrease in the applicable conversion rate.

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Notwithstanding the foregoing, if a conversion rate adjustment becomes effective on any ex-dividend date as described above, and a holder that has converted its notes on or after such ex-dividend date and on or prior to the related record date would be treated as the record holder of shares of our common stock as of the related conversion date as described under “— Settlement upon conversion” based on an adjusted conversion rate for such ex-dividend date, then, notwithstanding the foregoing conversion rate adjustment provisions, the conversion rate adjustment relating to such ex-dividend date will not be made for such converting holder. Instead, such holder will be treated as if such holder were the record owner of the shares of our common stock on an unadjusted basis and participate in the related dividend, distribution or other event giving rise to such adjustment.

Except as stated herein, we will not adjust the conversion rate for the issuance of shares of our common stock or any securities convertible into or exchangeable for shares of our common stock or the right to purchase shares of our common stock or such convertible or exchangeable securities.

As used in this section, “ex-dividend date” means the first date on which the shares of our common stock trade on the relevant stock exchange, regular way, without the right to receive the issuance, dividend or distribution in question, from us or, if applicable, from the seller of our common stock on the relevant stock exchange (in the form of due bills or otherwise) as determined by the relevant stock exchange, and “effective date” means the first date on which the shares of our common stock trade on the relevant stock exchange, regular way, reflecting the relevant share split or share combination, as applicable.

As used in this section, “record date” means, with respect to any dividend, distribution or other transaction or event in which the holders of our common stock (or other applicable security) have the right to receive any cash, securities or other property or in which our common stock (or such other security) is exchanged for or converted into any combination of cash, securities or other property, the date fixed for determination of holders of our common stock (or such other security) entitled to receive such cash, securities or other property (whether such date is fixed by our board of directors or a duly authorized committee thereof, statute, contract or otherwise).

We are permitted to increase the conversion rate of the notes by any amount for a period of at least 20 business days if our board of directors or a committee thereof determines that such increase would be in our best interest. We may also (but are not required to) increase the conversion rate to avoid or diminish income tax to holders of our common stock or rights to purchase shares of our common stock in connection with a dividend or distribution of shares (or rights to acquire shares) or similar event.

A holder may, in some circumstances, including a distribution of cash dividends to holders of our shares of common stock, be deemed to have received a distribution subject to U.S. federal income tax as a result of an adjustment or the nonoccurrence of an adjustment to the conversion rate. For a discussion of the U.S. federal income tax treatment of an adjustment to the conversion rate, see “Certain United States federal income and estate tax considerations”.

If we have a rights plan in effect upon conversion of the notes into common stock, you will receive, in addition to any shares of common stock received in connection with such conversion, the rights under the rights plan. However, if, prior to any conversion, the rights have separated from the shares of common stock in accordance with the provisions of the applicable rights plan, the conversion rate will be adjusted at the time of separation as if we distributed to all holders of

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our common stock, shares of our capital stock, evidences of indebtedness, assets, property, rights, options or warrants as described in clause (3) above, subject to readjustment in the event of the expiration, termination or redemption of such rights.

Adjustments to the conversion rate will be calculated to the nearest 1/10,000th of a share.

Recapitalizations, reclassifications and changes of our common stock

In the case of:

in each case as a result of which our common stock would be converted into, or exchanged for, cash, securities or other property (any such event, a “share exchange event” and any such cash, securities or other property, “reference property”, and the amount of reference property that a holder of one share of our common stock immediately prior to such transaction would have been entitled to receive upon the occurrence of such transaction, a “unit of reference property”), then we or the successor or purchasing company, as the case may be, will execute with the trustee, without the consent of the holders of the notes, a supplemental indenture providing that, at and after the effective time of the transaction, a holder’s right to convert a note will be changed into the right to convert such note into the amount of reference property that a holder of a number of shares of our common stock equal to the conversion rate immediately prior to such transaction would have been entitled to receive. However, at and after the effective time of the transaction:

Such supplemental indenture will also provide for anti-dilution and other adjustments that are as nearly equivalent as possible to the adjustments set described under “—Conversion rate

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adjustments” above. If the reference property in respect of any such transaction includes shares of stock, securities or other property or assets of a company other than us or the successor or purchasing corporation, as the case may be, in such transaction, such other company will also execute such supplemental indenture, and such supplemental indenture will contain such additional provisions to protect the interests of the holders, including the right of holders to require us to purchase their notes upon a fundamental change as described under “—Fundamental change permits holders to require us to purchase notes” below, as the board of directors (or an authorized committee thereof) reasonably considers necessary by reason of the foregoing. If the notes become convertible into reference property, we will notify the trustee and issue a press release containing the relevant information (and make the press release available on our website).

For purposes of the foregoing, if the transaction causes our common stock to be converted into, or exchanged for, the right to receive more than a single type of consideration (determined based in part upon any form of stockholder election), the amount and kind of reference property into which the notes will be convertible will be deemed to be the weighted average of the types and amounts of consideration received by the holders of our common stock that affirmatively make such an election. We will notify holders, the trustee and the conversion agent (if other than the trustee) of the weighted average as soon as practicable after such determination is made.

We will agree in the indenture not to become a party to any such transaction unless its terms are consistent with the foregoing.

Adjustments of prices

Whenever any provision of the indenture requires us to calculate the last reported sale prices, the daily VWAPs, the daily conversion values or the daily settlement amounts over a span of multiple days (including an observation period and, if applicable, the period for determining the “stock price” for purposes of a make-whole fundamental change), our board of directors or a committee thereof will make appropriate adjustments to each to account for any adjustment to the conversion rate that becomes effective, or any event requiring an adjustment to the conversion rate where the ex-dividend date, effective date or expiration date, as the case may be, of the event occurs, at any time during the period when the last reported sale prices, the daily VWAPs, the daily conversion values or the daily settlement amounts are to be calculated.

Adjustment to conversion rate upon conversion upon a make-whole fundamental change or a notice of redemption

If (A) the “effective date” (as defined below) of a “make-whole fundamental change” (as defined below) occurs prior to the maturity date of the notes or (B) on or after April 1, 2017, we give notice to the holders of our intent to redeem any or all of the notes in cash as provided under “—Optional redemption,” and a holder elects to convert its notes in connection with such make-whole fundamental change or redemption notice, as the case may be, we will, under certain circumstances, increase the conversion rate for the notes so surrendered for conversion by a number of additional shares of common stock (the “additional shares”), as described below.

A conversion of notes will be deemed for these purposes to be “in connection with” such make-whole fundamental change if the notice of conversion of the notes is received by the conversion

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agent from, and including, the effective date of the make-whole fundamental change up to, and including, the business day immediately prior to the related fundamental change purchase date (or, in the case of a make-whole fundamental change that would have been a fundamental change but for the proviso in clause (2) of the definition thereof, the 35th trading day immediately following the effective date of such make-whole fundamental change). A conversion of notes will be deemed for these purposes to be “in connection with” a redemption notice if the notice of conversion of the notes is received by the conversion agent from, and including, the date of the redemption notice until the close of business on the business day immediately preceding the redemption date.

A “make-whole fundamental change” means any transaction or event that constitutes a fundamental change defined below in clause (1), (2) or (4) under the definition of “fundamental change” in “—Fundamental change permits holders to require us to purchase notes”, after giving effect to any exceptions or exclusions from such definition, but without regard to the proviso in clause (2) of the definition thereof.

Upon surrender of notes for conversion in connection with a make-whole fundamental change, we will, at our option, satisfy our conversion obligation by physical settlement, cash settlement or combination settlement, as described under “—Conversion rights—Settlement upon conversion”. However, if the consideration for our common stock in any make-whole fundamental change described in clause (2) of the definition of fundamental change is composed entirely of cash, for any conversion of notes following the effective date of such make-whole fundamental change, the conversion obligation will be calculated based solely on the “stock price” (as defined below) for the transaction and will be deemed to be an amount of cash per $1,000 principal amount of converted notes equal to the conversion rate (including any adjustment as described in this section), multiplied by such stock price. In such event, the conversion obligation will be determined and paid to holders in cash on the third business day following the conversion date.

We will notify holders of the effective date of any make-whole fundamental change and issue a press release (and make the press release available on our website) announcing such effective date no later than five business days after such effective date.

The number of additional shares, if any, by which the conversion rate will be increased will be determined by reference to the table below, based on the date on which the make-whole fundamental change occurs or becomes effective or the date of the redemption notice, as the case may be (each an “effective date”), and the price (the “stock price”) paid (or deemed to be paid) per share of our common stock in the make-whole fundamental change or, in the case of a redemption as described below. If the holders of our common stock receive in exchange for their common stock only cash in a make-whole fundamental change described in clause (2) of the definition of fundamental change, the stock price shall be the cash amount paid per share. Otherwise, and in the case of a conversion upon notice of redemption, the stock price shall be the average of the last reported sale prices of our common stock over the five trading day period ending on, and including, the trading day immediately preceding the effective date of the make-whole fundamental change or the date on which we give the notice of redemption, as the case may be.

The stock prices set forth in the column headings of the table below will be adjusted as of any date on which the conversion rate of the notes is otherwise adjusted. The adjusted stock prices will equal the stock prices immediately prior to such adjustment, multiplied by a fraction, the numerator of which is the conversion rate immediately prior to the adjustment giving rise to the

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stock price adjustment and the denominator of which is the conversion rate as so adjusted. The number of additional shares will be adjusted in the same manner and at the same time as the conversion rate as set forth under “—Conversion rate adjustments”.

The following table sets forth the number of additional shares to be added to the conversion rate per $1,000 principal amount of notes in connection with a make-whole fundamental change or a redemption notice, as the case may be:

The exact stock prices and effective dates may not be set forth in the table above, in which case:

Notwithstanding the foregoing, in no event will the conversion rate per $1,000 principal amount of notes exceed 51.4138, subject to adjustment in the same manner as the conversion rate as set forth under “—Conversion rate adjustments”.

Our obligation to increase the conversion rate could be considered a penalty, in which case the enforceability thereof would be subject to general principles of reasonableness and equitable remedies.

Fundamental change permits holders to require us to purchase notes

If a “fundamental change” (as defined below in this section) occurs at any time, holders will have the right, at their option, to require us to purchase for cash all of their notes, or any portion of the principal thereof that is equal to $1,000 or an integral multiple of $1,000 on the fundamental change purchase date, which will be a date specified by us that is not less than 20 or more than 35 business days following the date of our fundamental change notice as described below or, if we fail to specify a fundamental change purchase date, the 35th business day following the date of our fundamental change notice (without prejudice to any rights or remedies holders may have on account of such failure).

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The fundamental change purchase price we are required to pay will be equal to 100% of the principal amount of the notes to be purchased, plus accrued and unpaid interest to, but excluding, the fundamental change purchase date (unless the fundamental change purchase date falls after a regular record date but on or prior to the interest payment date to which such regular record date relates, in which case we will instead pay the full amount of accrued and unpaid interest to the holder of record on such regular record date, and the fundamental change purchase price will be equal to 100% of the principal amount of the notes to be purchased).

A “fundamental change” will be deemed to have occurred at the time after the notes are originally issued if any of the following occurs:

A fundamental change as a result of either of clause (1) or clause (2) above will not be deemed to have occurred, however, if 90% or more of the consideration received or to be received by our common stockholders (excluding cash payments for fractional shares and cash payments made pursuant to dissenters’ appraisal rights) in connection with the transaction or transactions constituting the fundamental change consists of shares of capital stock or American Depositary Receipts traded on the New York Stock Exchange, the NASDAQ Global Market or the NASDAQ

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Global Select Market (or any of their respective successors) or which will be so traded when issued or exchanged in connection with the transaction that would otherwise be a fundamental change (these securities being referred to as “publicly traded securities”) and as a result of this transaction or transactions the notes become convertible into such publicly traded securities, excluding cash payments for fractional shares.

On or before the 20th business day after the occurrence of a fundamental change, we will provide to all holders of the notes and the trustee and paying agent a notice of the occurrence of the fundamental change and of the resulting purchase right. Such notice shall state, among other things:

Simultaneously with providing such notice, we will issue a press release containing this information (and make the press release available on our website).

To exercise the purchase right, a holder must deliver, on or before the business day immediately preceding the fundamental change purchase date, subject to extension to comply with applicable law, the notes to be purchased, duly endorsed for transfer, together with a written purchase notice and the form entitled “Form of Fundamental Change Purchase Notice” on the reverse side of the notes duly completed, to the paying agent. The purchase notice must include the following information:

If the notes are not in certificated form, the purchase notice given by each holder must comply with appropriate DTC procedures.

Holders may withdraw any purchase notice (in whole or in part) by a written notice of withdrawal delivered to the paying agent prior to the close of business on the business day immediately preceding the fundamental change purchase date. The notice of withdrawal shall include the following information:

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If the notes are not in certificated form, the withdrawal notice given by each holder must comply with appropriate DTC procedures.

We will be required to purchase the notes on the fundamental change purchase date, subject to extension to comply with applicable law. A holder of notes that has exercised the purchase right will receive payment of the fundamental change purchase price promptly following the later of the fundamental change purchase date or the time of book-entry transfer or the delivery of the notes. If the paying agent holds money sufficient to pay the fundamental change purchase price of the notes on the fundamental change purchase date, then the following shall occur:

In connection with any purchase offer pursuant to a fundamental change purchase notice, we will, if required do the following:

We will not be required to make an offer to purchase the notes upon a fundamental change if a third party makes the offer in the manner, at the times, and otherwise in compliance with the requirements set forth in the indenture applicable to an offer by us to purchase the notes upon a fundamental change and such third party purchases all notes validly tendered and not withdrawn upon such offer.

The purchase rights of the holders could discourage a potential acquirer of us. The fundamental change purchase feature, however, is not the result of management’s knowledge of any specific effort to obtain control of us by any means or part of a plan by management to adopt a series of anti-takeover provisions.

The term fundamental change is limited to specified transactions and may not include other events that might adversely affect our financial condition or the value of the notes. In addition, the requirement that we offer to purchase the notes upon a fundamental change may not protect holders in the event of a highly leveraged transaction, reorganization, merger or similar transaction involving us.

The definition of fundamental change includes a phrase relating to the sale, lease, or other transfer in one transaction or a series of transactions of “all or substantially all” of the consolidated assets of ours and our subsidiaries. There is no precise, established definition of the phrase “substantially all” under applicable law. Accordingly, the ability of a holder of the notes

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to require us to purchase its notes as a result of the sale, lease, or other transfer in one transaction or a series of transactions of less than all of the assets of ours and our subsidiaries may be uncertain. For the avoidance of doubt, the metric provided with respect to the definition of “substantially all of its assets” under “—Merger, consolidation or sale of assets” is not part of the definition of “fundamental change”.

If a fundamental change were to occur, we may not have enough funds to pay the fundamental change purchase price or be able to arrange for financing to pay the purchase price in connection with a tender of notes for purchase. Our ability to repurchase the notes for cash may be limited by the terms of our then existing borrowing arrangements or otherwise. See “Risk Factors—Risks related to an investment in the notes and our common stock—We may not have the ability to raise the funds necessary to purchase the notes upon a fundamental change, and our future debt may contain limitations on our ability to pay cash upon the repurchase of the notes.” If we fail to purchase the notes when required following a fundamental change, we will be in default under the indenture. In addition, we have, and may in the future incur, other indebtedness with similar change in control provisions permitting our holders to accelerate or to require us to purchase our indebtedness upon the occurrence of similar events or on some specific dates.

Optional redemption

We may not redeem the notes prior to April 5, 2017. On or after to April 5, 2017, we may redeem any or all of the notes, except for the notes that we are required to repurchase as provided under “—Fundamental change permits holders to require us to purchase notes,” in cash at the redemption price; provided that the last reported sale price of our common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending within 5 trading days immediately prior to the date of the redemption notice exceeds 130% of the applicable conversion price on each applicable trading day.

The redemption price for the notes to be redeemed on any redemption date will equal:

unless the redemption date falls after a regular record date but on or prior to the immediately succeeding interest payment date, in which case we will instead pay the full amount of accrued and unpaid interest to the holder of record as of the close of business on such regular record date and the redemption price will be 100% of the principal amount of notes to be redeemed. The redemption date must be a business day.

We will give notice of redemption not less than 30 nor more than 60 calendar days immediately preceding the redemption date to all holders of notes on the date of the redemption notice at their addresses shown in the register of the registrar, with a copy to the trustee and the paying agent. The redemption notice will state, among other things:

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We will issue a press release (and make the press release available on our website) announcing the redemption.

If we do not redeem all of the notes, the trustee will select the notes to be redeemed in principal amounts of $1,000 or integral multiples of $1,000 by lot, pro rata to the extent practicable or by another method the trustee routinely uses, and in each case to the extent permitted by DTC. If the trustee selects a portion of a holder’s notes for partial redemption and such holder converts a portion of such holder’s note, the converted portion will be deemed to be from the portion selected for redemption. If any notes are to redeemed in part only, we will issue new notes in principal amount equal to the unredeemed principal portion thereof.

With respect to any notes that are converted in connection with a redemption notice, we, under certain circumstances, will increase the conversion rate for the notes so surrendered for conversion by a number of additional shares as described under “—Conversion rights—Adjustment to shares delivered upon a conversion upon a make-whole fundamental change or a notice of redemption.” In addition, we will pay accrued and unpaid interest on such notes to the date of conversion as described under “—Conversion rights—conversion upon notice of redemption.”

No notes may be redeemed if the principal amount of the notes has been accelerated, and such acceleration has not been rescinded, on or prior to the redemption date.

Covenants

The indenture will contain the following principal covenants:

Limitation on liens

The Company will not incur, and will not permit any of its Subsidiaries to incur, any indebtedness for borrowed money secured by a mortgage, security interest, pledge, lien, charge or other similar encumbrance (collectively, “Liens”) upon (a) any Principal Property of the Company or any Principal Property of a Subsidiary or (b) any shares of stock or other equity interests or Indebtedness of any Subsidiary that owns a Principal Property (whether such Principal Property, shares of stock or other equity interests or Indebtedness is now existing or owned or hereafter created or acquired), in each case, unless prior to or at the same time, the notes (together with, at the option of the Company, any other indebtedness of the Company or any Subsidiary ranking equally in right of payment with the notes) are equally and ratably secured with or, at the option of the Company, prior to, such indebtedness.

Any Lien created for the benefit of the holders of the notes pursuant to the preceding sentence shall provide by its terms that such Lien shall be automatically and unconditionally released and discharged upon the release and discharge of such Lien.

The foregoing restriction does not apply, with respect to any person, to any of the following:

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Notwithstanding the foregoing restrictions, the Company and its Subsidiaries will be permitted to incur indebtedness secured by a Lien which would otherwise be subject to the foregoing restrictions without equally and ratably securing the notes, if any, provided that, after giving effect to such indebtedness, the aggregate amount of all indebtedness secured by Liens (not including Liens permitted under clauses (1) through (12) above), together with all attributable debt outstanding pursuant to the second paragraph of the “—Limitation on sale and leaseback transactions” covenant, does not exceed 15% of the Consolidated Net Tangible Assets of the Company calculated as of the date of the creation or incurrence of the Lien. The Company and its Subsidiaries also may, without equally and ratably securing the notes, create or incur Liens that extend, renew, substitute or replace (including successive extensions, renewals, substitutions or replacements), in whole or in part, any Lien permitted pursuant to the preceding sentence.

Limitation on sale and leaseback transactions

The Company will not directly or indirectly, and will not permit any of its Subsidiaries that own a Principal Property directly or indirectly to, enter into any sale and leaseback transaction for the sale and leasing back of any Principal Property, whether now owned or hereafter acquired, unless:

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Notwithstanding the restrictions set forth in the preceding paragraph, the Company and its Subsidiaries may enter into any sale and leaseback transaction which would otherwise be subject to the foregoing restrictions, if after giving effect thereto the aggregate amount of all attributable debt with respect to such transactions, together with all indebtedness outstanding pursuant to the last paragraph of the “—Limitation on liens” covenant already described, does not exceed 15% of the Consolidated Net Tangible Assets of the Company calculated as of the closing date of the sale and leaseback transaction.

Definitions

The indenture will contain the following defined terms:

“Attributable debt” means, with respect to any sale and leaseback transaction, at the time of determination, the lesser of (1) the sale price of the property so leased multiplied by a fraction the numerator of which is the remaining portion of the base term of the lease included in such transaction and the denominator of which is the base term of such lease, and (2) the total obligation (discounted to the present value at the implicit interest factor, determined in accordance with GAAP, included in the rental payments) of the lessee for rental payments (other than amounts required to be paid on account of property taxes as well as maintenance, repairs, insurance, water rates and other items which do not constitute payments for property rights) during the remaining portion of the base term of the lease included in such transaction.

“Consolidated Net Tangible Assets” means, as of the time of determination, the aggregate amount of the assets of the Company and the assets of its consolidated subsidiaries after deducting (1) all goodwill, trade names, trademarks, service marks, patents, unamortized debt discount and expense and other intangible assets and (2) all current liabilities, as reflected on the most recent consolidated balance sheet prepared by the Company in accordance with GAAP contained in an annual report on Form 10-K or a quarterly report on Form 10-Q timely filed or any amendment thereto (and not subsequently disclaimed as not being reliable by the Company) pursuant to the Exchange Act by the Company prior to the time as of which “Consolidated Net Tangible Assets” is being determined.

“Currency agreement” means in respect of a person any foreign exchange contract, currency swap agreement or other similar agreement designed to protect such person against fluctuations in currency values.

“GAAP” means generally accepted accounting principles set forth in the opinions and pronouncements of the Accounting Principles Board of the American Standards Board or in such other statements by such other entity as have been approved by a significant segment of the accounting profession.

“Guarantee” means any obligation, contingent or otherwise, of any person directly or indirectly guaranteeing any indebtedness of any other person and any obligation, direct or indirect, contingent or otherwise, of such person (1) to purchase or pay (or advance or supply funds for the purchase or payment of) such indebtedness of such other person (whether arising by virtue of partnership arrangements, or by agreement to keep well, to purchase assets, goods, securities or

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services, to take or pay or to maintain financial statement conditions or otherwise) or (2) entered into for purposes of assuring in any other manner the obligee of such indebtedness of the payment thereof or to protect such obligee against loss in respect thereof (in whole or in part); provided, however, that the term “guarantee” will not include endorsements for collection or deposit in the ordinary course of business. The term “guarantee,” when used as a verb, has a correlative meaning.

“Hedging obligation” means the obligations of any person pursuant to any interest rate agreement or currency agreement.

“Holder” means the person in whose name a note is registered on the security register books.

“Incur” means issue, assume, guarantee or otherwise become liable for Indebtedness.

“Indebtedness” means, with respect to any person, obligations of such person for borrowed money (including without limitation, indebtedness for borrowed money evidenced by notes, bonds, debentures or similar instruments).

“Interest rate agreement” means, in respect of a person, any interest rate swap agreement, interest rate cap agreement or other financial agreement or arrangement designed to protect such person against fluctuations in interest rates.

“Person” means any individual, corporation, partnership, limited liability company, joint venture, association, joint-stock company, trust, unincorporated organization or government or political subdivision thereof.

“Principal Property” means any domestic blast furnace or steel producing facility, or casters that are part of a plant that includes such a facility, in each case located in the United States, having a net book value in excess of 1% of Consolidated Net Tangible Assets at the time of determination.

“Refinance” means, in respect of any indebtedness, to refinance, extend, renew, refund, repay, prepay, redeem, defease or retire, or to issue other indebtedness in exchange or replacement for, such indebtedness. “Refinanced” and “Refinancing” shall have correlative meanings.

“Subsidiary” means, with respect to any person (the “parent”) at any date, any corporation, limited liability company, partnership, association or other entity owning a majority of the shares of securities or other interests having ordinary voting power for the election of directors or another governing body (other than securities or interests having such power only by reason of the happening of a contingency) are at the time beneficially owned directly or indirectly through one or more intermediaries, or both by the parent.

Merger, consolidation or sale of assets

The Company will not, in a single transaction or through a series of related transactions, consolidate or merge with or into any other person, or, directly or indirectly, sell or convey substantially all of its assets (as defined below) to another person or group of affiliated persons, except that the Company may consolidate or merge with, or sell or convey substantially all of its assets to another person if:

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For purposes of this covenant only, “substantially all of its assets” means, at any date, a portion of the non-current assets reflected in the Company’s consolidated balance sheet as of the end of the most recent quarterly period that represents at least 66 2/3% of the total reported value of such assets.

Upon such a succession, the Company will be relieved from any further obligations under the indenture.

Although these types of transactions are permitted under the indenture, certain of the foregoing transactions could constitute a fundamental change (as defined above) permitting each holder to require us to purchase the notes of such holder as described above.

Events of default

Each of the following is an event of default under the indenture:

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For a description of the remedies available to holders of the notes as a results of an event of default, see “Description of Debt Securities—Events of Default” in the accompanying prospectus.

If an event of default regarding the notes should occur and be continuing, either the trustee or the holders of not less than 25% in the principal amount of outstanding notes may declare the notes due and payable.

Holders of a majority in principal amount of the outstanding notes will be entitled to control certain actions of the trustee under the indenture and to waive certain past defaults regarding such notes. The trustee generally cannot be required by any of the holders of the notes to take any action, unless one or more of such holders shall have provided to the trustee security or indemnity reasonably satisfactory to it.

Before any holder of the notes may institute action for any remedy, except payment on such holder’s notes when due, the holders of not less than 25% in principal amount of the notes outstanding must request the trustee to take action. Holders must also offer and give the trustee satisfactory security and indemnity against liabilities incurred by the trustee for taking such action.

Notwithstanding the foregoing, the indenture will provide that, to the extent elected by us, the sole remedy for an event of default relating to the failure to comply with the reporting obligations in the indenture, which are described below under “—Reports” and for any failure to comply with the requirements of Section 314(a)(1) of the Trust Indenture Act will for the first 120 days after the occurrence of such an event of default consist exclusively of the right to receive additional interest on the notes at an annual rate equal to 0.50% of the principal amount of the notes. If we so elect, such additional interest will accrue on all outstanding notes from and including the date on which the event of default relating to the failure to comply with the reporting obligations in the indenture or the failure to comply with the requirements of Section 314(a)(1) of the Trust Indenture Act first occurs to but not including the 120th day thereafter (or such earlier date on which such event of default is cured or waived by the holders of a majority in principal amount of the outstanding notes). On such 120th day (or earlier, if the event of default relating to the reporting obligations under the indenture or the failure to comply with the requirements of Section 314(a)(1) of the Trust Indenture Act is cured or waived by the holders of a majority in principal amount of the outstanding notes prior to such 120th day), such additional interest will cease to accrue and, if the event of default relating to reporting obligations or the failure to comply with Section 314(a)(1) of the Trust Indenture Act has not been cured or waived prior to such 120th day, the notes will be subject to acceleration as provided above. The provisions of the indenture described in this paragraph will not affect the rights of holders of notes in the event of the occurrence of any other event of default. In the event we do not elect to pay the additional interest upon an event of default in accordance with this paragraph, the notes will be subject to acceleration as provided above.

In order to elect to pay the additional interest on the notes as the sole remedy during the first 120 days after the occurrence of an event of default relating to the failure to comply with the reporting obligations in the indenture or the failure to comply with Section 314(a)(1) of the Trust Indenture Act in accordance with the immediately preceding paragraph, we must notify all holders of notes and the trustee and paying agent of such election on or before the close of business on the date on which such event of default first occurs.

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Modification and amendment

In addition to the provisions of the indenture described under “Description of the Debt Securities—Modification of the Indentures” in the accompanying prospectus, the Company and the trustee may, without the consent of the holders of the notes, modify the indenture or enter into or modify any supplemental indenture to conform the provisions of the indenture to the “Description of notes” section in this prospectus supplement.

In addition to the provisions of the indenture described under “Description of the Debt Securities—Modification of the Indentures” in the accompanying prospectus, the following provisions of the notes may not be modified without the consent of each holder of an outstanding note affected thereby:

Defeasance

The defeasance provisions described in the second paragraph under “Description of the Debt Securities—Satisfaction and Discharge; Defeasance and Covenant Defeasance” in the accompanying prospectus will not apply to the notes.

Calculations in respect of notes

Except as otherwise provided above, we will be responsible for making all calculations called for under the notes or the indenture. These calculations include, but are not limited to, determinations of the last reported sale prices of our common stock, daily VWAPs, daily conversion values, daily settlement amounts, accrued interest payable on the notes and the conversion rate of the notes. We will make all these calculations in good faith and, absent manifest error, our calculations will be final and binding on the holders of the notes. We will provide a schedule of our calculations to each of the trustee and the conversion agent, and each of the trustee and the conversion agent is entitled to rely conclusively upon the accuracy of our calculations without independent verification. The trustee will forward our calculations to any holder of the notes upon the request of that holder.

No stockholder rights for holders of notes

Holders of notes, as such, will not have any rights as stockholders of the company (including, without limitation, voting rights and rights to receive any dividends or other distributions on our common stock).

Reports

The indenture governing the notes provides that any documents or reports that we are required to file with the SEC pursuant to Section 13 or 15(d) of the Exchange Act must be delivered by us to the trustee within 15 days after the same are required to be filed with the SEC.

Trustee

The Bank of New York Mellon will be the trustee, security registrar, paying agent and conversion agent for the notes. The Bank of New York Mellon, in each of its capacities, including without

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limitation as trustee, security registrar, paying agent and conversion agent, assumes no responsibility for the accuracy or completeness of the information concerning us or our affiliates or any other party contained in this document or the related documents or for any failure by us or any other party to disclose events that may have occurred and may affect the significance or accuracy of such information.

We may maintain banking relationships in the ordinary course of business with the trustee and its affiliates.

Governing law

The indenture provides that it and the notes will be governed by, and construed in accordance with, the laws of the State of New York.

Exchange and transfer

You may exchange or transfer the notes in accordance with the indenture. You will not be required to pay a service charge to exchange or transfer the notes, but you may be required to pay for any tax or other governmental charge associated with the exchange or transfer. The exchange or transfer will only be made if the transfer agent is satisfied with your proof of ownership. See “—Book-entry issuance.”

Paying and paying agents

The Bank of New York Mellon will act as our paying agent for the notes. We may choose to pay interest by mailing checks or making wire or other electronic funds transfers. Regardless of who acts as the paying agent, all money paid by us to a paying agent that remains unclaimed at the end of two years after the amount is due to note holders will be repaid to us. After that two-year period, you may look only to us for payment and not to the trustee, any other paying agent or anyone else. We may also arrange for additional payment offices and may cancel or change these offices, including any use of the trustee’s corporate trust office. We may appoint or change any paying agent without prior notice to any note holder.

Book-entry issuance

The notes will be represented by one or more global notes that will be deposited with and registered in the name of The Depository Trust Company, or DTC, or its nominee. We will not issue certificated notes to you, except in the limited circumstances described below. Each global note will be issued to DTC, which will keep a computerized record of its participants whose clients have purchased the notes. Each participant will then keep a record of its own clients. Unless it is exchanged in whole or in part for a certificated note, a global note may not be transferred. DTC, its nominees and their successors may, however, transfer a global note as a whole to one another, and these transfers are required to be recorded on our records or a register to be maintained by the trustee.

Beneficial interests in a global note will be shown on, and transfers of beneficial interests in the global note will be made only through, records maintained by DTC and its participants. DTC has provided us with the following information: DTC is a limited purpose trust company organized under the New York Banking Law, a “banking organization” within the meaning of the New York Banking Law, a member of the Federal Reserve System, a “clearing corporation” within the

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meaning of the New York Uniform Commercial Code and a “clearing agency” registered under the provisions of Section 17A of the Exchange Act. DTC holds securities that its direct participants deposit with DTC. DTC also records the settlements among direct participants of securities transactions, such as transfers and pledges, in deposited securities through computerized records for direct participants’ accounts. This book-entry system eliminates the need to exchange certificated securities. Direct participants include securities brokers and dealers, banks, trust companies, clearing corporations and certain other organizations.

DTC’s book-entry system is also used by other organizations such as securities brokers and dealers, banks and trust companies that work through a direct participant. The rules that apply to DTC and its participants are on file with the SEC.

DTC is owned by a number of its direct participants and by the New York Stock Exchange, Inc., the American Stock Exchange, Inc. and the National Association of Securities Dealers, Inc.

When you purchase notes through the DTC system, the purchases must be made by or through a direct participant, which will receive credit for the notes on DTC’s records. When you actually purchase the notes, you will become their beneficial owner. Your ownership interest will be recorded only on the direct or indirect participants’ records. DTC will have no knowledge of your individual ownership of the notes. DTC’s records will show only the identity of the direct participants and the principal amount of the notes held by or through them. You will not receive a written confirmation of your purchase or sale or any periodic account statement directly from DTC. You should instead receive these from your direct or indirect participant. As a result, the direct or indirect participants are responsible for keeping accurate account of the holdings of their customers. The trustee will wire payments on the notes to DTC’s nominee. We and the trustee will treat DTC’s nominee as the owner of each global note for all purposes. Accordingly, we, the trustee and any paying agent will have no direct responsibility or liability to pay amounts due on a global note to you or any other beneficial owners in that global note.

We understand that is DTC’s current practice, upon receipt of any payment of distributions or liquidation amounts, to proportionately credit direct participants’ accounts on the payment date based on their holdings. In addition, we understand that it is DTC’s current practice to pass through any consenting or voting rights to such participants by using an omnibus proxy. Those participants will, in turn, make payments to and solicit votes from you, the ultimate owner of notes, based on their customary practices. Payments to you will be the responsibility of the participants and not of DTC, the trustee or the Company.

Notes represented by one or more global notes will be exchangeable for certificated notes with the same terms in authorized denominations only if:

If a global note is exchanged for certificated notes, the trustee will keep the registration books for the notes at its corporate office and follow customary practices and procedures regarding those certificated notes

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Description of common stock

Please read the information discussed under the heading “Description of capital stock” beginning on page 13 of the accompanying prospectus, which the following information supplements and, in the event of inconsistencies, supersedes. The following description does not purport to be complete and, except as noted above, should be read in conjunction with the description in the prospectus.

General

The authorized capital stock of U. S. Steel consists of 40 million shares of preferred stock, without par value, and 400 million shares of common stock with a par value of $1.00 per share. As of March 15, 2013, there were no shares of preferred stock outstanding and 144,283,311 shares of common stock outstanding.

Stock transfer agent and registrar

Wells Fargo Bank, N.A., 161 N. Concord Exchange, South St. Paul, MN 55075 serves as the transfer agent and registrar for our common stock. The telephone number for Wells Fargo Shareowner Services is (866) 433-4801.

Delaware law, our certificate of incorporation and by-laws contain provisions that may have an anti-takeover effect

Certain provisions of Delaware law and our certificate of incorporation could make more difficult or delay a change in control of U. S. Steel by means of a tender offer, a proxy contest or otherwise and the removal of incumbent directors. These provisions are intended to discourage certain types of coercive takeover practices and inadequate takeover bids, even though such a transaction may offer our stockholders the opportunity to sell their stock at a price above the prevailing market price. Our board of directors believes that these provisions are appropriate to protect the interests of U. S. Steel and its stockholders.

Delaware law. We are governed by the provisions of Section 203 of the Delaware General Corporation Law. In general, Section 203 prohibits a public Delaware corporation from engaging in a “business combination” with an “interested stockholder” for a period of three years following the time that the person became an interested stockholder, unless:

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A “business combination” includes mergers, asset sales or other transactions resulting in a financial benefit to the stockholder. An “interested stockholder” is a person who, together with affiliates and associates, owns (or within three years did own) 15% or more of the corporation’s voting stock.

Certificate of incorporation and by-laws. Our certificate of incorporation provides that our board of directors is classified into three classes of directors, each class consisting of approximately one-third of the directors. Each director serves a three-year term, with a different class of directors up for election each year. Under Delaware law, directors of a corporation with a classified board may be removed only for cause unless the corporation’s certificate of incorporation provides otherwise. Our certificate of incorporation does not provide otherwise. Board classification could prevent a party who acquires control of a majority of U. S. Steel’s outstanding voting stock from obtaining control of our board of directors until the second annual stockholders’ meeting following the date that party obtains control.

Our certificate of incorporation also provides that any action required or permitted to be taken by our stockholders must be effected at a duly called annual or special meeting and may not be taken by written consent.

Our by-laws provide that special meetings of stockholders may be called only by the board of directors and not by the stockholders. Our by-laws include advance notice and informational requirements and time limitations on any director nomination or any new proposal that a stockholder wishes to make at a meeting of stockholders. In general, a stockholder’s notice of a director nomination or proposal will be timely if delivered or mailed to our Secretary at our principal executive offices not less than 90 days and not more than 120 days prior to the first anniversary of the date on which the proxy materials for the preceding year’s annual meeting were first mailed. These provisions may preclude stockholders from bringing matters before a meeting or from making nominations for directors at these meetings.

Our certificate of incorporation and by-laws do not include a provision for cumulative voting for directors. Under cumulative voting, a minority stockholder holding a sufficient percentage of a class of shares may be able to ensure the election of one or more directors.

Our certificate of incorporation provides for the issuance of preferred stock, at the discretion of our board of directors, from time to time, in one or more series, without further action by our stockholders, unless approval of our stockholders is deemed advisable by our board of directors or required by applicable law, regulation or stock exchange listing requirements. In addition, our authorized but unissued shares of our common stock will be available for issuance from time to time at the discretion of our board of directors without the approval of our stockholders, unless such approval is deemed advisable by our board of directors or required by applicable law, regulation or stock exchange listing requirements. One of the effects of the existence of authorized, unissued and unreserved shares of our common stock and preferred stock could be to enable our board of directors to issue shares to persons friendly to current management that could render more difficult or discourage an attempt to obtain control of U. S. Steel by means of a merger, tender offer, proxy contest or otherwise, and thereby protect the continuity of our

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management. Such additional shares also could be used to dilute the stock ownership of persons seeking to obtain control of U. S. Steel.

Our certificate of incorporation provides that vacancies in our board of directors may be filled only by the affirmative vote of a majority of the remaining directors. The certificate of incorporation also provides that directors may be removed from office only with cause. These provisions preclude stockholders from removing directors without cause and filling vacancies with their own nominees.

Certain provisions described above may have the effect of delaying stockholder actions with respect to certain business combinations. As such, the provisions could have the effect of discouraging open market purchases of our shares of common stock because such provisions may be considered disadvantageous by a stockholder who desires to participate in a business combination.

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Certain United States federal income and estate tax considerations

This section describes the material United States federal income and estate tax consequences of owning the notes we are offering and, in the case of non-United States holders (as defined below), the shares of our common stock into which the notes may be converted. It applies only to a holder that acquires notes in the offering at the offering price listed on the cover page hereof and that holds its notes or, in the case of non-United States holders, shares of our common stock, as capital assets within the meaning of Section 1221 of the Internal Revenue Code of 1986, as amended (the “Code”). This section does not apply to a holder that is a member of a class of holders subject to special rules, such as: