Exhibit 23

            Consent of Independent Registered Public Accounting Firm

The Board of Directors
Cass Information Systems, Inc.:

We consent to the incorporation by reference in the registration statements
(Nos. 333-44499, 333-91456, and 333-91568) on Form S-8 of Cass Information
Systems, Inc. of our reports dated March 9, 2007, with respect to the
consolidated balance sheets of Cass Information Systems, Inc. as of December 31,
2006 and 2005, and the related consolidated statements of income, cash flows,
and shareholders' equity and comprehensive income for each of the years in the
three-year period ended December 31, 2006, management's assessment of the
effectiveness of internal control over financial reporting as of December 31,
2006 and the effectiveness of internal control over financial reporting as of
December 31, 2006, which reports appear in the December 31, 2006 annual report
on Form 10-K of Cass Information Systems, Inc.

As discussed in notes 1 and 13 to the consolidated financial statements, as of
December 31, 2006, the Company adopted Statement of Financial Accounting
Standard No. 158, Employers' Accounting for Defined Benefit Pension and Other
Postretirement Plans.

St. Louis, Missouri
March 9, 2007


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