[LOGO] Cass
       Information
       Systems, Inc.

                               September 15, 2005

Cicely D. Luckey
Branch Chief
Mail Stop 4561
United States Securities and Exchange Commission
Washington, D. C. 20549

            Re:   Cass Information Systems, Inc.
                  Form 10-K for the year ended December 31, 2004
                  Form 10-Q for the quarter ended March 31, 2005
                  File No. 333-44497

Dear Ms. Luckey:

Please accept these responses to the comments contained in your August 26, 2005
letter regarding the aforementioned filings and our initial response to your
comments dated August 2, 2005. If you need further clarification on any
response, please feel free to call me at the telephone number listed below.

      1.    We have considered your response to comment 1 and question your
            classification of other income items (i.e., gain on the sales of
            investment securities) within revenues. These amounts should be
            presented below net interest income after the provision for loan
            losses pursuant to Rule 9-04 of Regulation S-X. Please advise or
            revise future filings accordingly to reclassify these amounts.

Per Regulation S-X Rule 5-01 "This article [5] shall be applicable to financial
statements filed for all persons except - ... (d) Bank holding companies and
banks (see Article 9)." Cass Information Systems, Inc. ("Cass"), by virtue of
its ownership of Cass Commercial Bank, is a bank holding company. We therefore
look to Article 9 Rule 9-04 for the Income Statement line items required by the
Commission on applicable filings.

All income items listed as items 1 through 13 in Rule 9-04 are contained in our
Income Statement as presented in the aforementioned filings. Items 1 through 12
relate to net interest income after provision for loan losses and Item 13, which
is labeled "Other Income" relates to all noninterest income. Given that the
total amount reported under Item 13 (noninterest income) for Cass Information
Systems, Inc. greatly exceeds the sum of Items 1 through 12 (net interest
income), the placement of Item 13 and its label "Other Income" obscures the
operating results of Cass and has caused confusion with investors in the past.



Therefore, we placed Item 13 above Items 1 through 12 and adjusted the heading
to "Fee Revenue and Other Income". Other than these adjustments to the placement
and heading, the content directly corresponds to Rule 9-04.

In addition, per Rule 9-04, under Item 13 "Other Income", companies must
"Disclose separately any one of the following amounts, or any other item of
other income, which exceed one percent of the aggregate of total interest income
and other income. The remaining amounts may be shown as one amount, except for
investment securities gains or losses which shall be shown separately regardless
of size." Investment securities gains or losses are also referred to under Item
13 "Other Income" under (h) "Investment securities gains or losses." We have
therefore included investment securities gains or losses under Item 13.

      2.    We have reviewed your response to our prior comment 3 [accounting
            for an investment with a 19.99% equity interest under the cost
            method]. Given the investee has "performed poorly during the past
            few years", it is unclear why you believe the extension of a credit
            line does not create some level of dependence on your Company as the
            investor. This combined with your board representation appears to
            indicate you may have significant influence over this investee.
            Further, majority ownership interest by another investor does not
            necessary preclude the ability to exercise significant influence.
            Please further advise us your consideration of the facts and
            circumstances that lead you to believe that you have no significant
            influence over this investee.

The investment of Cass in Imaging Acceptance Corporation ("IAC") is accounted
for under the cost method due to the absence of significant influence of Cass on
IAC. The factors considered in this determination were derived mainly from
Accounting Principles Board ("APB") Opinion No. 18 (As amended), but also from
other authoritative literature and guidance issued by the Securities and
Exchange Commission and its staff.

The first factor evaluated is Cass' ownership interest in IAC. Cass has a 19.99%
voting stock interest in IAC. APB Opinion 18, paragraph 17 states "...an
investment of less than 20% of the voting stock of an investee should lead to a
presumption that an investor does not have the ability to exercise significant
influence unless such ability can be demonstrated." The remaining 80.01% is held
by IAC Acquisitions LLC ("Majority Holder") and is not distributed among smaller
investors with no controlling interest. The Financial Accounting Standards Board
issued Interpretation No. 35 (As Amended) ("FIN 35") to clarify the criteria for
applying the equity method. FIN 35, paragraph 4 provides examples of indicators
that an investor may be unable to exercise significant influence over the
investee, even if the investor owns more than 20% of the voting stock. Paragraph
4c states "Majority ownership of the investee is concentrated among a small
group of shareholders who operate the investee without regard to the views of
the investor." Although the relationship with the Majority Holder is not
acrimonious, the Majority Holder has its own management team in place running
the day-to-day operations of IAC and has the wherewithal, intent and ability to
provide funding in excess of the equity represented by its voting stock. The
Company's Certificate of Incorporation also provides additional rights, detailed
below, to the Majority Holder that significantly limit the influence that Cass
has on IAC.


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The second factor considered is whether the extension of a line of credit by
Cass to IAC increases the influence of Cass on IAC to a significant level. This
line of credit replaced a line that had been provided by a nonaffiliated
commercial bank. Cass, as a bank holding company, routinely provides lines of
credit to companies that have similar financing requirements. The purpose of the
line is to provide working capital to IAC and the terms and conditions are
comparable to other lines of credit offered by Cass to its customers. The line
is collateralized by receivables, inventory and equipment. It revolves according
to a borrowing base and the interest rate floats over prime. The line contains
the usual rights and privileges granted a secured lender but does not serve as
equity, does not include voting rights and does not fund IAC losses. The
Majority Holder provides 50% of the funding for and has a 50% interest in this
line of credit. In addition, the Majority Holder also provides significant
funding directly to IAC. As of July 31, 2005, unrelated financial institutions
provided $2,020,000, or 22% of the IAC debt outstanding, Cass provided
$1,602,000, or 17%, and the Majority Holder provided $5,563,000, or 61%. IAC is
certainly not dependent on Cass for funding. In determining if the Cass line of
credit increased Cass' influence over IAC, it is noted that loans made in the
normal course of business do not generally provide the lender with significant
influence over debtors. In fact, influence exerted on management can imperil the
collateral position of the lender, render guarantees invalid and lead to other
lender liability issues.

The third factor considered is board representation. Although Cass has
representation on the IAC Board, it is a minority representation with one seat
out of five. One seat is currently vacant. All other directors are officers of
IAC and are affiliated with the Majority Holder. The Cass board seat exists
solely in recognition of Cass' minority interest. Cass has no right to
representation on any committee of the Board, and is not a member of any
committee. As a result, Cass has limited influence in the policy-making process
of IAC, which is effectively controlled by the Majority Holder. It should be
noted that, if the vacant Board seat were to be filled, the Majority Holder, by
reason of its control of a majority of the voting shares, would be able to fill
it. This, combined with the rights granted to the Majority Holder in IAC's
Certificate of Incorporation, significantly limits the influence that Cass has
on IAC.

The following additional factors, obtained from APB Opinion No. 18, are also
reviewed to determine whether they could lead to a conclusion that Cass has
significant influence over IAC.

      1.    Shared Management Personnel

            There is no interchange of management between Cass and IAC. The
            President/CEO of IAC is employed by a company owned by the Majority
            Holder. The Majority Holder provides a staff to IAC for consulting
            on technology, marketing and management issues. The financial
            management is controlled by the Majority Holder. Finally, all
            decisions regarding operations, staffing, marketing and all other
            key areas are made by the staff and representatives of the Majority
            Holder.


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      2.    Specific approval requirements for operating decisions, policy,
            budgets, selection and compensation of management, etc.

            Cass has no approval rights for any of these decisions, all of which
            are controlled by the Majority Holder. The Majority Holder, by the
            Certificate of Incorporation and Investment Agreements has other
            rights and privileges. For example, The Majority Holder must approve
            IAC's performance and capital budgets, any indebtedness or
            incurrence of liens over $100,000, any transactions with affiliates,
            the appointment or dismissal of IAC's CEO, the employment
            arrangements of IAC's CEO and senior management or the creation of
            any subsidiary. FIN 35 provides another example of an indicator that
            an investor may be unable to exert significant influence over an
            investee even if the investor owns 20% or more of the voting stock
            in paragraph 4c which states "The investor and investee sign an
            agreement under which the investor surrenders significant rights as
            a shareholder." The granting of these rights to the Majority Holder
            significantly limits the influence that Cass has over IAC.

      3.    Significant intercompany transactions including administrative
            support, human resources, business development, finance, etc.

            Cass has no such intercompany transactions with IAC.

      4.    Significant source of customers or supplies.

            Cass is not a source of customers or supplies to IAC and IAC is not
            a source of customers or supplies to Cass.

      5.    Economic Dependence

            As discussed above, other than the 19.99% equity investment, the
            only economic relationship of Cass with IAC is the secured line of
            credit that could be provided by another financial institution. The
            Majority Holder not only participates in 50% of this line, but also
            provides a majority of the IAC debt outstanding.

      6.    Technological Dependence

            There is no technology transfer.

In summary, and in light of all the facts and circumstances related to the
investment in IAC, we do not believe that Cass has significant influence over
IAC for the following reasons:

      o     IAC has only two equity investors. Cass holds 19.99% of IAC's voting
            stock and IAC Acquisitions LLC holds 80.01% of IAC's voting stock.

      o     While Cass has provided a line of credit to IAC, the Majority Holder
            provides 50% of the funding for the line and has a 50% interest in
            the line. In addition to this line, the Majority Holder also lends
            directly to IAC, on a subordinate basis. As of July 31, 2005, Cass
            provided only 17% of IAC debt outstanding. IAC is not dependent on
            Cass for funding.


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      o     Cass holds one of five IAC board seats. One seat is currently
            vacant. The vacant seat could be filled by the Majority Holder due
            to its control. The other three seats are held by the Majority
            Holder.

      o     Cass provides no management or other personnel to IAC; the Majority
            Holder provides and effectively controls management.

      o     Cass has no specific approval or veto rights with respect to
            decisions of IAC (other than the right to elect one director by
            virtue of its ownership of IAC stock). The Certificate of
            Incorporation provides that most significant corporate matters must
            be approved by the Majority Holder.

      o     There is no customer/supplier relationship between Cass and IAC or
            any technology transfer. Although Cass provides a line of credit for
            a minority of IAC's debt, IAC is not dependent on Cass for financial
            support. Cass believes that, because of the quality of IAC's
            receivables, inventory and equipment collateral, alternative credit
            could be obtained by IAC from an unrelated financial institution.

If you have any questions or require any additional information please call me
at (314) 506-5502.

                                   Sincerely,


                                   /s/ Eric H. Brunngraber

                                   Eric H. Brunngraber
                                   Chief Financial Officer