
<PAGE>
 
                                                                    Exhibit 25.1

                      SECURITIES AND EXCHANGE COMMISSION
                            Washington, D.C. 20549

                           -------------------------

                                 F O R M   T-1

STATEMENT OF ELIGIBILITY AND QUALIFICATION UNDER THE TRUST INDENTURE ACT OF 1939
                               OF A CORPORATION
                         DESIGNATED TO ACT AS TRUSTEE

                           -------------------------

   CHECK IF AN APPLICATION TO DETERMINE ELIGIBILITY OF A TRUSTEE PURSUANT TO
                            SECTION 305(B)(2)____.
                                        
                   CHASE BANK OF TEXAS, NATIONAL ASSOCIATION
              (Exact name of trustee as specified in its charter)

Organized under the laws of                           74-0800980
the United States of America                        (I.R.S. employer
(State of incorporation                            identification no.)
if not a National Bank)

712 Main Street                                          77002
HOUSTON, TEXAS                                        (Zip Code)
(Address of principal executive offices)

Lee Boocker
Chase Bank of Texas, National Association
712 Main Street, 26th Floor
Houston, Texas 77002
(713) 216-2448
(Name, address and telephone
number of agent for service)

                           -------------------------

                                  ONEOK, INC.
              (Exact name of obligor as specified in its charter)



Oklahoma                                              73-1520922

(State or other jurisdictions of                    (I.R.S. employer
incorporation or organization)                    identification nos.)
 
100 West Fifth Street
Tulsa, Oklahoma                                          74103
(Address of obligor's principal executive offices)     (Zip Code)


                         $500,000,000 DEBT SECURITIES
                      (Title of the indenture securities)

                                       1
<PAGE>
 
Item 1.    General Information.

           Furnish the following information as to the Trustee:

           (a)  Name and address of each examining or supervising authority to
                which it is subject.

           Name                                                   Address
           -------------------------------------------------------------------
           Comptroller of the Currency                        Washington, D.C.
           Board of Governors of the Federal Reserve System   Washington, D.C.
           Federal Deposit Insurance Corporation              Washington, D.C.
 
           (b)  Whether it is authorized to exercise corporate trust powers.

           Yes, the trustee is authorized to exercise corporate trust powers.


Item 2.    Affiliations with the Obligor.

           If the obligor is an affiliate of the Trustee, describe each such
           affiliation. (See Note on Page 3)

           The obligor is not an affiliate of the trustee.


Item 16.   List of Exhibits.

           List below all exhibits filed as part of this statement of
           eligibility:

           Exhibit 1.  A copy of the Articles of Association of the Trustee as
                       now in effect.
           Exhibit 2.  A copy of the certificate of authority of the Trustee to
                       commence business.
           Exhibit 3.  A copy of the authorization of the Trustee to exercise
                       corporate trust powers.
           Exhibit 4.  A copy of the existing bylaws of the Trustee.
           Exhibit 5.  Not Applicable.
           Exhibit 6.  The consents of the United States Institutional trustees
                       required by Section 321(b) of the Trust Indenture Act of
                       1939.
           Exhibit 7.  A copy of the latest report of condition of the Trustee
                       published pursuant to law or the requirements of its
                       supervising or examining authority.
           Exhibit 8.  Not Applicable.
           Exhibit 9.  Not Applicable.

                                       2
<PAGE>
 
                      NOTE REGARDING INCORPORATED EXHIBIT

Effective January 20, 1998, the name of the Trustee was changed from Texas
Commerce Bank National Association to Chase Bank of Texas, National Association.
The exhibits incorporated herein by reference, except for Exhibit 7, were filed
under the former name of the Trustee.

     Exhibit 1.  Incorporated by reference to exhibit bearing the same
                 designation and previously filed with the 
                 Securities and Exchange Commission as exhibit
                 to the Form S-3 File No. 33-56195.   
     Exhibit 2.  Incorporated by reference to exhibit bearing the same
                 designation and previously filed with the 
                 Securities and Exchange Commission as exhibit
                 to the Form S-3 File No. 33-42814.   
     Exhibit 3.  Incorporated by reference to exhibit bearing the same
                 designation and previously filed with the 
                 Securities and Exchange Commission as exhibit
                 to the Form S-11 File No. 33-25132.   
     Exhibit 4.  Incorporated by reference to exhibit bearing the same
                 designation and previously filed with the 
                 Securities and Exchange Commission as exhibit
                 to the Form S-3 File No. 33-65055.   
     Exhibit 6.  Incorporated herewith.
     Exhibit 7.  Incorporated by reference to exhibit bearing the same
                 designation and previously filed with the 
                 Securities and Exchange Commission as exhibit
                 to the Form S-3 File No. 333-63747.  

Note:  The answer to Item 2 is based in part on information provided or
       confirmed by the obligor. The accuracy and completeness of such
       information is hereby disclaimed by the Trustee.

                                       3
<PAGE>
 
                                 SIGNATURE


  Pursuant to the requirements of the Trust Indenture Act of 1939, the Trustee,
Chase Bank of Texas, National Association, a national banking association
organized and existing under the laws of the United States of America, has duly
caused this statement of eligibility to be signed on its behalf by the
undersigned, thereunto duly authorized, all in the City of Dallas, and State of
Texas, on the 15th day of April 1999.



                                 CHASE BANK OF TEXAS, NATIONAL ASSOCIATION



                                 By: /s/ JOHN G. JONES       
                                    -------------------------------------------
                                 Name:   John G. Jones      
                                 Title:  Vice President


                                       4
<PAGE>
 
                                 EXHIBIT 6


Securities and Exchange Commission
Washington, D.C. 20549

Gentlemen:

  The undersigned is trustee under an indenture between ONEOK, Inc., an Oklahoma
corporation (the "Company") and Chase Bank of Texas, National Association
(formerly known as Texas Commerce Bank National Association), as Trustee,
entered into in connection with the issuance of the Corporation's Debt
Securities.

  In accordance with Section 321(b) of the Trust Indenture Act of 1939, the
undersigned hereby consents that reports of examinations of the undersigned,
made by Federal or State authorities authorized to make such examinations, may
be furnished by such authorities to the Securities and Exchange Commission upon
its request therefor.

                                  CHASE BANK OF TEXAS, NATIONAL ASSOCIATION


                                  By: /s/ JOHN G. JONES       
                                     --------------------------------------
                                  Name:   John G. Jones      
                                  Title:  Vice President
                                  Date:   April 15, 1999

                                       5
