6,900,000 Shares Common Stock UNDERWRITING AGREEMENT

The Company meets the requirements for use of Form S-3 and a registration statement (Registration No. 333-82717) on Form S-3, as amended, relating to the Shares, including a preliminary prospectus and such amendments to such registration statement as may have been required to the date of this Agreement, has been prepared by the Company under the provisions of the Securities Act of 1933 (the “Act”), and the rules and regulations (collectively referred to as the “Rules and Regulations”) of the Securities and Exchange Commission (the “Commission”) thereunder, and has been filed with the Commission. The term “preliminary prospectus” as used herein means a preliminary prospectus as contemplated by Rule 430 or Rule 430A (“Rule 430A”) of the Rules and Regulations included at any time as part of the registration statement. Copies of such registration statement and amendments and of each related preliminary prospectus have been delivered to the Underwriter. The term “Registration Statement” means the registration statement described above, as amended at the time it became effective (the “Effective Date”), including financial statements and all exhibits and any information deemed to be included by Rule 430A or Rule 434 of the Rules and Regulations. If the Company files a registration statement to register a portion of the Shares and relies on Rule 462(b) of the Rules and Regulations for such registration statement to become effective upon filing with the Commission (the “Rule 462 Registration Statement”), then any reference to the “Registration Statement” shall be deemed to include the Rule 462 Registration Statement, as amended from time to time. The Company will file with the Commission a prospectus supplement (the “Prospectus Supplement”)

relating to the Shares pursuant to Rule 424 or Rule 434 under the Act. The term “Prospectus” means the form of final prospectus included in the Registration Statement at the Effective Date, as amended and supplemented prior to the date of this Agreement and as supplemented by the Prospectus Supplement, and shall be deemed to include the “electronic Prospectus” provided for use in connection with the offering of the Shares as contemplated by Section 4(l) of this Agreement. Any reference herein to the Registration Statement, any preliminary prospectus or the Prospectus shall be deemed to refer to and include (i) the documents incorporated by reference therein pursuant to Item 12 of Form S-3 that were filed under the Securities Exchange Act of 1934 (the “Exchange Act”), on or before the Effective Date or the date of such preliminary prospectus or the Prospectus, as the case may be, and (ii) any copy thereof filed with the Commission pursuant to its Electronic Data Gathering, Analysis and Retrieval System (“EDGAR”). Any reference herein to the terms “amend,” “amendment” or “supplement” with respect to the Registration Statement, any preliminary prospectus or the Prospectus shall be deemed to refer to and include the filing of any document under the Exchange Act after the Effective Date, or the date of any preliminary prospectus or the Prospectus, as the case may be, and deemed to be incorporated therein by reference.

The Company has not received, and has no notice of, any order of the Commission preventing or suspending the use of any preliminary prospectus, or instituting proceedings for that purpose. Each preliminary prospectus and the Prospectus when filed complied in all material respects with the Act and, if filed by electronic transmission pursuant to EDGAR (except as may be permitted by Regulation S-T under the Act), was identical to the copy thereof delivered to the Underwriter for use in connection with the offer and sale of the Shares. On the Effective Date, the date the Prospectus is first filed with the Commission pursuant to Rule 424(b) of the Rules and Regulations, at all times subsequent to and including the Closing Date and when any post-effective amendment to the Registration Statement becomes effective or any amendment or supplement to the Prospectus is filed with the Commission, the Registration Statement and the Prospectus (as amended or as supplemented if the Company shall have filed with the Commission any amendment or supplement thereto), including the financial statements included or incorporated by reference in the Prospectus, did or will comply with all applicable provisions of the Act, the Exchange Act, the rules and regulations thereunder (the “Exchange Act Rules and Regulations”) and the Rules and Regulations and will contain all statements required to be stated therein in accordance with the Act, the Exchange Act, the Exchange Act Rules and Regulations and the Rules and Regulations. On the Effective Date and when any post-effective amendment to the Registration Statement becomes effective, no part of the Registration Statement or any such amendment did or will contain any untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary in order to make the statements therein not misleading. At the Effective Date, the date the Prospectus or any amendment or supplement to the Prospectus is filed with the Commission and at the Closing Date and, if later, the Option Closing Date, the Prospectus did not and will not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not

misleading. The foregoing representations and warranties in this Section 3(b) do not apply to any statements or omissions made in reliance on and in conformity with information relating to the Underwriter furnished in writing to the Company by the Underwriter specifically for inclusion in the Registration Statement or Prospectus or any amendment or supplement thereto. For all purposes of this Agreement, the amounts of the selling concession and reallowance set forth in the Prospectus constitute the only information relating to the Underwriter furnished in writing to the Company by the Underwriter specifically for inclusion in the Registration Statement or the Prospectus. The Company has not distributed any offering material in connection with the offering or sale of the Shares other than the Registration Statement, the preliminary prospectus, the Prospectus or any other materials, if any, permitted by the Act.

The only subsidiaries (as defined in the Rules and Regulations) of the Company are the subsidiaries named on Schedule II hereto (the “Subsidiaries”). The Company and each of its Subsidiaries is, and at the Closing Date will be, a corporation, limited liability company, general partnership or limited partnership duly organized, validly existing and in good standing under the laws of its jurisdiction of incorporation or organization. The Company and each of its Subsidiaries have, and at the Closing Date will have, full power and authority to conduct all the activities conducted by it, to own or lease all the assets owned or leased by it and to conduct its business as described in the Registration Statement and the Prospectus. The Company and each of its Subsidiaries is, and at the Closing Date will be, duly licensed or qualified to do business and in good standing as a foreign corporation, limited liability company, general partnership or limited partnership in all jurisdictions in which the nature of the activities conducted by it or the character of the assets owned or leased by it makes such licensing or qualification necessary, except to the extent that the failure to so qualify, be licensed or be in good standing would not have a material adverse effect on the condition (financial or otherwise), earnings, cash flow, business affairs or business prospects of the Company and its Subsidiaries, considered as one enterprise (a “Material Adverse Effect”). Except as set forth on Schedule II hereto, all of the outstanding shares of capital stock, capital interests or partnership interests of the Subsidiaries have been duly authorized and validly issued and, as to capital stock, are fully paid and non-assessable, and are owned by the Company free and clear of all security interests, liens, encumbrances and claims whatsoever. Except for (i) the stock of or interests in the Subsidiaries disclosed on Schedule II hereto and (ii) as disclosed in the Registration Statement and the Prospectus, the Company does not

own, and at the Closing Date will not own, directly or indirectly, any shares of stock or any other equity or long-term debt securities of any corporation or have any equity interest in any firm, partnership, joint venture, association or other entity. Complete and correct copies of the certificate of incorporation and of the by-laws or other organizational documents of the Company and each of its significant subsidiaries (as defined in Rule 1-02(w) of Regulation S-X of the Rules and Regulations) and all amendments thereto have been delivered to the Underwriter, and no changes therein will be made subsequent to the date hereof and prior to the Closing Date or, if later, the Option Closing Date.

The financial statements and schedules included or incorporated by reference in the Registration Statement or the Prospectus, and any amendment or supplement thereto, present fairly the consolidated financial condition of the Company, as of the date thereof and the consolidated results of operations and cash flows of the Company for the period covered thereby, in conformity with generally accepted accounting principles applied on a consistent basis throughout the entire period involved. KPMG LLP (the “Accountant”), the accounting firm that has certified the financial statements and schedules included or incorporated by reference in the Registration Statement or the Prospectus, and any amendment or supplement thereto, is an independent public accounting firm within the meaning of the Act and the Rules and Regulations and the Accountant is not in violation of the auditor independence requirements of Section 201 of the Sarbanes-Oxley Act of 2002 (the “Sarbanes-Oxley Act”) with respect to the Company. Except as otherwise included or

incorporated by reference in the Registration Statement or the Prospectus, there are no pro forma financial statements or other pro forma financial information required to be included or incorporated by reference in the Registration Statement or the Prospectus. The pro forma financial information of the Company included in the documents incorporated by reference into the Registration Statement present fairly the information contained therein, have been prepared in accordance with the Commission’s rules and guidelines with respect to pro forma financial statements in accordance with Article 11 of Regulation S-X of the Exchange Act and have been properly presented on the bases described therein, and the assumptions used in the preparation thereof are reasonable and the adjustments used therein are appropriate to give effect to the transactions and circumstances referred to therein. No other financial statements or schedules of the Company are required by the Act, the Exchange Act or the Rules and Regulations to be included or incorporated by reference in the Registration Statement or the Prospectus. The Company’s ratios of earnings to fixed charges and earnings to combined fixed charges and preferred stock dividend requirements set forth in Exhibits 12.1 and 12.2 to the Registration Statement have been calculated in compliance with Item 503(d) of Regulation S-K under the Act.

No consent, approval, authorization or order of, or any filing or declaration with, any court or governmental agency or body is required in connection with the authorization, issuance, transfer, sale or delivery of the Shares by the Company, in connection with the execution, delivery and performance of this Agreement by the Company or in connection with the taking by the Company of any action

contemplated hereby, except such (i) as have been obtained under the Act or the Rules and Regulations, (ii) as may be required under state securities or Blue Sky laws or the by-laws and rules of the National Association of Securities Dealers, Inc. (the “NASD”) in connection with the purchase and distribution by the Underwriter of the Shares and (iii) that the failure to obtain would not result in a Material Adverse Effect.

All legal or governmental proceedings, affiliate transactions, contracts, licenses, agreements, leases or documents of a character required to be described in the Registration Statement or the Prospectus or to be filed as an exhibit to the Registration Statement have been so described or filed as required. All such contracts to which the Company or any Subsidiary is a party have been duly authorized, executed and delivered by the Company or such Subsidiary, constitute valid and binding agreements of the Company or such Subsidiary and are

enforceable against the Company or such Subsidiary in accordance with the terms thereof, subject to the effect of bankruptcy, insolvency, reorganization, receivership, moratorium and other laws affecting the rights and remedies of creditors generally and general equitable principles and subject to any principles of public policy limiting the rights to enforce any indemnification provisions contained herein and therein.

In the ordinary course of its business, the Company conducts a periodic review of the effect of Environmental Laws on the business, operations and properties of the Company and its Subsidiaries, in the course of which it identifies and evaluates associated costs and liabilities (including, without limitation, any capital or operating expenditures required for clean-up, closure of properties or compliance with

Environmental Laws or any permit, license or approval, any related constraints on operating activities and any potential liabilities to third parties). Except as set forth in the Registration Statement and the Prospectus there are no costs and liabilities associated with or arising in connection with Environmental Laws or Hazardous Materials as currently in effect (including, without limitation, costs of compliance therewith) which would, singly or in the aggregate have a Material Adverse Effect.

During the 90-day period beginning on the date of this Agreement, the Company will not without the prior written consent of the Underwriter (which consent may be withheld at the sole discretion of the Underwriter), directly or indirectly, sell, offer, contract or grant any option to sell, pledge, transfer or establish an open “put equivalent position” within the meaning of Rule 16a-1(h) under the Exchange Act, or otherwise dispose of or transfer, or file with the Commission a registration statement under the Act relating to, any shares of Common Stock or securities convertible into or exchangeable for any shares of Common Stock, or publicly disclose the intention to make any such offer, sale, pledge, transfer, disposition or filing, except for (i) issuances pursuant to employee or director compensation plans existing on the date of this Agreement, including issuances pursuant to the exercise of stock options

outstanding on the date of this Agreement, (ii) grants of employee stock options pursuant to the terms of a plan in effect on the date of this Agreement, (iii) issuances pursuant to the exercise of such stock options, (iv) the filing of registration statements on Form S-8 and amendments thereto in connection with such stock options or the Company’s employee stock purchase plans in existence on the date of this Agreement, (v) issuances pursuant to direct stock purchase or dividend reinvestment plans in place on the date of this Agreement and (vi) the issuance of shares of Common Stock or options in acquisitions in which the acquiror of such shares or options agrees to the foregoing restrictions.

Since the respective dates as of which information is given in the Registration Statement and the Prospectus, there shall have been no litigation or other proceeding instituted against the Company or any of its Subsidiaries or any of their respective officers or directors in their capacities as such, before or by any federal, state or local court, commission, regulatory body, administrative agency or other governmental body, domestic or foreign, in which litigation or proceeding an unfavorable ruling,

decision or finding would materially and adversely affect the business, properties, business prospects, condition (financial or otherwise) or results of operations of the Company and its Subsidiaries taken as a whole.

At the Closing Date and, as to the Option Shares, the Option Closing Date, there shall be furnished to the Underwriter an accurate certificate, dated the date of its delivery, signed by each of the Chief Executive Officer, President or a Vice

President and the Chief Financial Officer of the Company, in form and substance satisfactory to the Underwriter, to the effect that:

requested as to the accuracy and completeness at the Closing Date and the Option Closing Date of any statement in the Registration Statement or the Prospectus or any documents filed under the Exchange Act and deemed to be incorporated by reference into the Prospectus, as to the accuracy at the Closing Date and the Option Closing Date of the representations and warranties of the Company herein, as to the performance by the Company of its obligations hereunder, or as to the fulfillment of the conditions concurrent and precedent to the obligations hereunder of the Underwriter.

The Company will indemnify and hold harmless the Underwriter, the directors, officers, employees and agents of the Underwriter and each person, if any, who controls the Underwriter within the meaning of Section 15 of the Act or Section 20 of the Exchange Act from and against any and all losses, claims, liabilities, expenses and damages (including, but not limited to, any and all investigative, legal and other

expenses reasonably incurred in connection with, and any and all amounts paid in settlement of, any action, suit or proceeding between any of the indemnified parties and any indemnifying parties or between any indemnified party and any third party, or otherwise, or any claim asserted), as and when incurred, to which the Underwriter, or any such person, may become subject under the Act, the Exchange Act or other federal or state statutory law or regulation, at common law or otherwise, insofar as such losses, claims, liabilities, expenses or damages arise out of or are based on (i) any untrue statement or alleged untrue statement of a material fact contained in any preliminary prospectus, the Registration Statement or the Prospectus or any amendment or supplement to the Registration Statement or the Prospectus or in any documents filed under the Exchange Act and deemed to be incorporated by reference into the Prospectus, or in any application or other document executed by or on behalf of the Company or based on written information furnished by or on behalf of the Company filed in any jurisdiction in order to qualify the Shares under the securities laws thereof or filed with the Commission, (ii) the omission or alleged omission to state in such document a material fact required to be stated in it or necessary to make the statements in it not misleading or (iii) any act or failure to act or any alleged act or failure to act by the Underwriter in connection with, or relating in any manner to, the Shares or the offering contemplated hereby, and which is included as part of or referred to in any loss, claim, liability, expense or damage arising out of or based upon matters covered by clause (i) or (ii) above (provided that the Company shall not be liable under this clause (iii) to the extent it is finally judicially determined by a court of competent jurisdiction that such loss, claim, liability, expense or damage resulted directly from any such acts or failures to act undertaken or omitted to be taken by the Underwriter through its gross negligence or willful misconduct); provided that the Company will not be liable to the extent that such loss, claim, liability, expense or damage arises from the sale of the Shares in the offering to any person by the Underwriter and is based on an untrue statement or omission or alleged untrue statement or omission made in reliance on and in conformity with information relating to the Underwriter furnished in writing to the Company by the Underwriter expressly for inclusion in the Registration Statement, any preliminary prospectus or the Prospectus. This indemnity agreement will be in addition to any liability that the Company might otherwise have.

Any party that proposes to assert the right to be indemnified under this Section 8 will, promptly after receipt of notice of commencement of any action against such party in respect of which a claim is to be made against an indemnifying party or parties under this Section 8, notify the indemnifying party of the commencement of such action, enclosing a copy of all papers served, but the omission so to notify the indemnifying party will not relieve it from any liability that it may have to any indemnified party under the foregoing provisions of this Section 8 unless, and only to the extent that, such omission results in the forfeiture of substantive rights or defenses by the indemnifying party. If any such action is brought against any indemnified party and it notifies the indemnifying party of its commencement, the indemnifying party will be entitled to participate in and, to the extent that it elects by delivering written notice to the indemnified party promptly after receiving notice of the commencement of the action from the indemnified party to assume the defense of the action, with counsel satisfactory to the indemnified party, and after notice from the indemnifying party to the indemnified party of its election to assume the defense, the indemnifying party will not be liable to the indemnified party for any legal or other expenses except as provided below and except for the reasonable costs of investigation subsequently incurred by the indemnified party in connection with the defense. The indemnified party will have the right to employ its own counsel in any such action, but the fees, expenses and other charges of such counsel will be at the expense of the indemnified party unless (i) the employment of counsel by the indemnified party has been authorized in writing by the indemnifying party, (ii) the indemnified party has reasonably concluded (based on advice of counsel) that there may be legal defenses available to it or other indemnified parties that are different from or in addition to those available to the indemnifying party, (iii) a conflict or potential conflict exists (based on advice of counsel to the indemnified party) between the indemnified party and the indemnifying party (in which case the indemnifying party will not have the right to direct the defense of such action on behalf of the indemnified party) or (iv) the indemnifying party has not in fact employed counsel to assume the defense of such action within a reasonable time after receiving notice of the commencement of the action, in each of which cases the reasonable fees, disbursements and other charges of counsel will be at the expense of the indemnifying party or parties. It is understood that the indemnifying party shall not, in connection with any proceeding or related proceedings in the same jurisdiction, be liable for the reasonable fees, disbursements and other charges of more than one separate firm admitted to practice in such jurisdiction at any one time for all such indemnified party or parties. All such fees, disbursements and other charges will be reimbursed by the indemnifying party promptly as they are incurred. An indemnifying party will not be liable for any settlement of any action or claim effected without its written consent (which consent will not be unreasonably withheld). No indemnifying party shall, without the prior written consent of each indemnified party, settle or compromise or consent to the entry of any judgment in any pending or threatened claim, action or proceeding relating to the matters contemplated by this Section 8 (whether or not any indemnified party is a party

thereto), unless such settlement, compromise or consent includes an unconditional release of each indemnified party from all liability arising or that may arise out of such claim, action or proceeding. Notwithstanding any other provision of this Section 8(c), if at any time an indemnified party shall have requested an indemnifying party to reimburse the indemnified party for fees and expenses of counsel, such indemnifying party agrees that it shall be liable for any settlement effected without its written consent if (1) such settlement is entered into more than 45 days after receipt by such indemnifying party of the aforesaid request, (2) such indemnifying party shall have received notice of the terms of such settlement at least 30 days prior to such settlement being entered into and (3) such indemnifying party shall not have reimbursed such indemnified party in accordance with such request prior to the date of such settlement.

In order to provide for just and equitable contribution in circumstances in which the indemnification provided for in the foregoing paragraphs of this Section 8 is applicable in accordance with its terms but for any reason is held to be unavailable from the Company or the Underwriter, the Company and the Underwriter shall contribute to the total losses, claims, liabilities, expenses and damages (including any investigative, legal and other expenses reasonably incurred in connection with, and any amount paid in settlement of, any action, suit or proceeding or any claim asserted, but after deducting any contribution received by the Company from persons other than the Underwriter, such as persons who control the Company within the meaning of the Act, officers of the Company who signed the Registration Statement and directors of the Company, who also may be liable for contribution) to which the Company and the Underwriter may be subject in such proportion as shall be appropriate to reflect the relative benefits received by the Company on the one hand and the Underwriter on the other. The relative benefits received by the Company on the one hand and the Underwriter on the other shall be deemed to be in the same proportion as the total net proceeds from the offering (before deducting expenses) received by the Company bear to the total underwriting discounts and commissions received by the Underwriter as set forth in the table on the cover page of the Prospectus. If, but only if, the allocation provided by the foregoing sentence is not permitted by applicable law, the allocation of contribution shall be made in such proportion as is appropriate to reflect not only the relative benefits referred to in the foregoing sentence but also the relative fault of the Company, on the one hand, and the Underwriter, on the other, with respect to the statements or omissions that resulted in such loss, claim, liability, expense or damage, or action in respect thereof, as well as any other relevant equitable considerations with respect to such offering. Such relative fault shall be determined by reference to whether the untrue or alleged untrue statement of a material fact or the omission or alleged omission to state a material fact related to information supplied by the Company or the Underwriter, the intent of the parties and their relative knowledge, access to information and opportunity to correct or prevent such statement or omission. The Company and the Underwriter agree that it would not be just and equitable if contributions pursuant to this Section 8(d) were to be determined by pro rata allocation or by any other method of allocation which does not take into account the equitable considerations referred to herein. The amount paid or payable by an indemnified party as a result of the loss,

claim, liability, expense or damage, or action in respect thereof, referred to above in this Section 8(d) shall be deemed to include, for purpose of this Section 8(d), any legal or other expenses reasonably incurred by such indemnified party in connection with investigating or defending any such action or claim. Notwithstanding the provisions of this Section 8(d), the Underwriter shall not be required to contribute any amount in excess of the underwriting discounts and commissions received by it and no person found guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of the Act) will be entitled to contribution from any person who was not guilty of such fraudulent misrepresentation. For purposes of this Section 8(d), any person who controls a party to this Agreement within the meaning of the Act will have the same rights to contribution as that party, and each officer of the Company who signed the Registration Statement will have the same rights to contribution as the Company, subject in each case to the provisions hereof. Any party entitled to contribution, promptly after receipt of notice of commencement of any action against such party in respect of which a claim for contribution may be made under this Section 8(d), will notify any such party or parties from whom contribution may be sought, but the omission so to notify will not relieve the party or parties from whom contribution may be sought from any other obligation it or they may have under this Section 8(d). Except for a settlement entered into pursuant to the last sentence of Section 8(c) hereof, no party will be liable for contribution with respect to any action or claim settled without its written consent (which consent will not be unreasonably withheld).

Termination. The obligations of the Underwriter under this Agreement may be terminated at any time on or prior to the Closing Date (or, with respect to the Option Shares, on or prior to the Option Closing Date), by notice to the Company from the Underwriter if, prior to delivery and payment for the Shares (or the Option Shares, as the case may be), in the sole judgment of the Underwriter, (a) there has been, since the respective dates as of which information is given in the Registration Statement and the Prospectus, any material adverse change or any development involving a prospective change, which has had or is reasonably likely to have a Material Adverse Effect; (b) trading in any of the equity securities of the Company shall have been suspended by the Commission, the NASD or the New York Stock Exchange; (c) trading in securities generally on the New York Stock Exchange or the Nasdaq National Market shall have been suspended or limited or minimum or maximum prices shall have been generally established on such exchange or automated quotation system, or additional material governmental restrictions, not in force on the date of this Agreement, shall have been imposed upon trading in securities generally by the New York Stock Exchange or The Nasdaq Stock Market or by order of the Commission or the NASD or any court or other governmental authority; (d) a general banking moratorium shall have been declared by federal or New York or Oklahoma State authorities; (e) there shall have occurred any

outbreak or escalation of national or international hostilities or any crisis or calamity, or any change in the United States or international financial or securities markets, or any substantial change or development involving a prospective substantial change in national or international political, financial or economic conditions, as in the judgment of the Underwriter is material and adverse and makes it impractical or inadvisable to market the Shares in the manner and on the terms described in the Prospectus or to enforce contracts for the sale of securities; (f) any downgrading, or placement on any watch list for possible downgrading, in the rating of the Company’s debt securities by any “nationally recognized statistical rating organization” (as defined for purposes of Rule 436(g) under the Exchange Act); (g) the taking of any action by any governmental body or agency in respect of its monetary or fiscal affairs that in the judgment of the Underwriter has a material adverse effect on the securities markets in the United States; or (h) the Company shall have sustained a loss by strike, fire, flood, earthquake, accident or other calamity of such character as in the judgment of the Underwriter may interfere materially with the business and operations of the Company regardless of whether of not such loss shall have been insured. Any termination pursuant to this Section 9 shall be without liability on the part of (i) the Company to the Underwriter, except that the Company shall be obligated to reimburse the expenses of the Underwriter pursuant to Section 4 and 6 hereof, (ii) the Underwriter to the Company or (iii) of any party hereto to any other party except that the provisions of Section 8 shall at all times be effective and shall survive such termination.

CITIGROUP GLOBAL MARKETS INC.

Acting as Underwriter

By:

    /s/ Scott Sanders

Name: Scott Sanders

Title: Director

Underwriter

Citigroup Global Markets Inc.

TOTAL

Subsidiary

Mid Continent Market Center, Inc.

ONEOK Sayre Storage Company

OkTex Pipeline Company

ONEOK Gas Transportation, L.L.C.

ONEOK Gas Storage Holdings, Inc.

ONEOK Texas Gas Storage, L.P.

ONEOK WesTex Transmission, L.P.

ONEOK Gas Storage, L.L.C.

ONEOK Palo Duro Pipeline Company, Inc.

ONEOK Services Company

ONEOK Technology Company

ONEOK Energy Marketing and Trading Company, II

Kansas Gas Marketing Company

ONEOK Energy Marketing and Trading Company, L.P.

ONEOK Energy Marketing Holdings, Inc.

ONEOK Energy Marketing Company

ONEOK Leasing Company

ONEOK Parking Company

ONEOK Field Services Company

ONEOK Bushton Processing, Inc.

Blue Moon Holdings, L.L.C.

ONEOK Field Services Holdings, Inc.

ONEOK Texas Field Services, L.P.

ONEOK Gas Processing, L.L.C.

ONEOK International, Inc.

ALPHA Transmission Company

Oklahoma Natural Energy Services Company

ONEOK Gas Gathering, L.L.C.

Potato Hills Gas Gathering System (general partnership)

ONEOK Kansas Company

Oasis Acquisition Corporation

Kansas Gas Service Company

Sycamore Gas System (general partnership)

Fox Plant, L.L.C.

ONEOK Midstream Gas Supply, L.L.C.

ONEOK NGL Marketing, L.P.

Kansas Gas Supply Corporation

ONEOK WesTex Gas Pipeline, Inc.

Subsidiary

ONEOK Texas Resources, Inc.

ONEOK Energy Resources Company

ONEOK Energy Resources Holdings, Inc.

ONEOK Texas Energy Holdings, LLC

ONEOK Texas Energy Resources, L.P.

TGS Rio, L.L.C.

ONEOK Energy Services Canada, Ltd.

Subsidiaries Acquired from Southern Union

Mercado Gas Services Inc.

ONEOK Transmission Company

ONEOK International Investments, Inc.

ONEOK Energy International, Inc.

ONEOK Propane Company

Energia Estrella de Sur, S.A. de C.V.

Compañia Nacional de Gas S.A. de C.V.

Construcciones, Instalaciones y Asesorías, S.A. de C.V.

Gas Servicios Del Norte de Mexico S. De R.L. De C.V.

Materiales y Aparatos, S.A. de C.V.

Salart, S.A. de C.V.

Servicios Corporativos Phenix, S.C.

CITIGROUP GLOBAL MARKETS INC.

By:

Name:

Title:

Printed Name of Holder

By:

Signature

Printed Name of Person Signing