BOK Financial Corporation
Exhibit 99.11


                        CERTIFICATION OF PERIODIC REPORT

I, Steven E. Nell, Executive Vice President and Chief Financial Officer of BOK
Financial Corporation ("BOK Financial), certify, pursuant to Section 906 of the
Sarbanes-Oxley Act of 2002, 18 U.S.C. Section 1350, that:

(1)      the Annual Report on Form 10-K of BOK Financial for the year
         ended December 31, 2002 (the "Report") fully complies with the
         requirements of Section 13 (a) or 15 (d)); and

(2)      the information contained in the Report fairly presents, in all
         material respects, the financial condition and results of operations of
         the company.

A signed  original of this  written  statement  required by Section 906 has been
provided to BOK  Financial  Corporation  and will be  retained by BOK  Financial
Corporation  and furnished to the  Securities  Exchange  Commission or its staff
upon request.

Dated: March 25, 2003



                                                      /s/ Steven E. Nell
                                                      ------------------------
                                                      Steven E. Nell
                                                      Executive Vice President
                                                      Chief Financial Officer
                                                      BOK Financial Corporation



                        CERTIFICATION OF PERIODIC REPORT

I, Stanley A. Lybarger, President and Chief Executive Officer of BOK Financial
Corporation ("BOK Financial"), certify, pursuant to Section 906 of the
Sarbanes-Oxley Act of 2002, 18 U.S.C. Section 1350, that:

(1) the Annual Report on Form 10-K of BOK Financial for the year
         ended December 31, 2002 (the "Report") fully complies with the
         requirements of Section 13 (a) or 15 (d)); and

(2)      the information contained in the Report fairly presents, in all
         material respects, the financial condition and results of operations of
         the company.

A signed  original of this  written  statement  required by Section 906 has been
provided to BOK  Financial  Corporation  and will be  retained by BOK  Financial
Corporation  and furnished to the  Securities  Exchange  Commission or its staff
upon request.

Dated: March 25, 2003


                                                      /s/ Stanley A. Lybarger
                                                      -----------------------
                                                      Stanley A. Lybarger
                                                      President
                                                      Chief Executive Officer
                                                      BOK Financial Corporation