Exhibit 99.1

                            CERTIFICATION PURSUANT TO
                             10 U.S.C. SECTION 1350,
                             AS ADOPTED PURSUANT TO
                  SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Quarterly Report of Cass Information Systems, Inc. ("the
Company") on Form 10-Q for the period ended June 30, 2002 as filed with the
Securities and Exchange Commission on the date hereof (the "Report"), I,
Lawrence A. Collett, Chief Executive Officer of the Company, certify, pursuant
to 18 U.S.C. ss. 1350, as adopted pursuant to ss. 906 of the Sarbanes-Oxley Act
of 2002, that:

       (1)    The Report fully complies with the requirements of section 13(a)
              or 15(d) of the Securities Act of 1934; and

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


         /s/ Lawrence A. Collett
- ----------------------------------------
           Lawrence A. Collett
   Chairman and Chief Executive Officer
             August 8, 2002