<PAGE>
Firstar Family of Funds
MERCANTILE MUTUAL FUNDS, INC.
(the "Company")
Trust Shares and Trust II Shares
of the
Treasury Money Market Portfolio, Money Market
Portfolio, Tax-Exempt Money Market Portfolio,
U.S. Government Securities Portfolio, Intermediate
Corporate Bond Portfolio, Bond Index Portfolio,
Government & Corporate Bond Portfolio,
Short-Intermediate Municipal Portfolio, Missouri
Tax-Exempt Bond Portfolio, National Municipal Bond
Portfolio, Balanced Portfolio, Equity Income Portfolio,
Equity Index Portfolio, Growth & Income Equity
Portfolio, Growth Equity Portfolio, Small Cap Equity
Portfolio, Small Cap Equity Index Portfolio and
International Equity Portfolio
Supplement dated September 26, 2000
to Prospectus dated March 31, 2000
Management of the International Equity Portfolio
------------------------------------------------
Clay Finlay Inc. ("Clay Finlay") serves as sub-adviser to the Company's
International Equity Portfolio (the "Portfolio"). Prior to 5:00 p.m. EDT on
September 25, 2000, Clay Finlay was an indirect subsidiary of United Asset
Management Corporation ("UAM"). At 5:00 p.m. EDT on September 25, 2000, Old
Mutual plc ("Old Mutual"), a public limited company based in the United Kingdom,
acquired over 90% of the outstanding stock of UAM pursuant to a tender offer, as
a result of which Clay Finlay is now an indirect subsidiary of Old Mutual. This
transaction constituted an assignment of, and automatically terminated, the
existing Sub-Advisory Agreement between Firstar Investment Research & Management
Company, LLC ("FIRMCO") and Clay Finlay with respect to the Portfolio. On
September 25, 2000, FIRMCO and Clay Finlay entered into an Interim Sub-Advisory
Agreement with respect to the Portfolio, which had been approved by the Board of
Directors of the Company at a meeting held on August 2, 2000. This action was
in accordance with the terms and conditions of Rule 15a-4 under the Investment
Company Act of 1940, as amended. Under Rule 15a-4, an adviser (or sub-adviser)
can serve pursuant to an interim advisory (or sub-advisory) agreement for up to
150 days while a fund seeks shareholder approval of a new investment advisory
(or sub-advisory agreement).
At a meeting held on July 11, 2000, the Board of Directors of the Company
approved a new Sub-Advisory Agreement between FIRMCO and Clay Finlay with
respect to the Portfolio. A Special Meeting of Shareholders of the Portfolio has
been scheduled for October 13, 2000 to consider and vote on the new Sub-Advisory
Agreement. Shareholders of record of the Portfolio as of the close of business
on August 28, 2000 are entitled to notice of, and to vote at,
<PAGE>
the Special Meeting. The sub-advisory fees earned by Clay Finlay under the
Interim Sub-Advisory Agreement will be held in an interest-bearing escrow
account at the Fund's custodian, Firstar Bank, N.A., and will be paid to Clay
Finlay if shareholders of the Portfolio approve the new Sub-Advisory Agreement.
2
<PAGE>
Firstar Family of Funds
MERCANTILE MUTUAL FUNDS, INC.
(the "Company")
Institutional Shares
of the
Treasury Money Market Portfolio, Money Market Portfolio,
U.S. Government Securities Portfolio,
Intermediate Corporate Bond Portfolio,
Bond Index Portfolio, Government &
Corporate Bond Portfolio,
Balanced Portfolio, Equity Income Portfolio,
Equity Index Portfolio, Growth & Income Equity
Portfolio, Growth Equity Portfolio, Small Cap Equity
Portfolio, Small Cap Equity Index Portfolio and
International Equity Portfolio
Supplement dated September 26, 2000
to Prospectus dated March 31, 2000
Management of the International Equity Portfolio
------------------------------------------------
Clay Finlay Inc. ("Clay Finlay") serves as sub-adviser to the Company's
International Equity Portfolio (the "Portfolio"). Prior to 5:00 p.m. EDT on
September 25, 2000, Clay Finlay was an indirect subsidiary of United Asset
Management Corporation ("UAM"). At 5:00 p.m. EDT on September 25, 2000, Old
Mutual plc ("Old Mutual"), a public limited company based in the United Kingdom,
acquired over 90% of the outstanding stock of UAM pursuant to a tender offer, as
a result of which Clay Finlay is now an indirect subsidiary of Old Mutual. This
transaction constituted an assignment of, and automatically terminated, the
existing Sub-Advisory Agreement between Firstar Investment Research & Management
Company, LLC ("FIRMCO") and Clay Finlay with respect to the Portfolio. On
September 25, 2000, FIRMCO and Clay Finlay entered into an Interim Sub-Advisory
Agreement with respect to the Portfolio, which had been approved by the Board of
Directors of the Company at a meeting held on August 2, 2000. This action was
in accordance with the terms and conditions of Rule 15a-4 under the Investment
Company Act of 1940, as amended. Under Rule 15a-4, an adviser (or sub-adviser)
can serve pursuant to an interim advisory (or sub-advisory) agreement for up to
150 days while a fund seeks shareholder approval of a new investment advisory
(or sub-advisory agreement).
At a meeting held on July 11, 2000, the Board of Directors of the Company
approved a new Sub-Advisory Agreement between FIRMCO and Clay Finlay with
respect to the Portfolio. A Special Meeting of Shareholders of the Portfolio has
been scheduled for October 13, 2000 to consider and vote on the new Sub-Advisory
Agreement. Shareholders of record of the Portfolio as of the close of business
on August 28, 2000 are entitled to notice of, and to vote at, the Special
Meeting. The sub-advisory fees earned by Clay Finlay under the Interim Sub-
<PAGE>
Advisory Agreement will be held in an interest-bearing escrow account at the
Fund's custodian, Firstar Bank, N.A., and will be paid to Clay Finlay if
shareholders of the Portfolio approve the new Sub-Advisory Agreement.
-2-
<PAGE>
Firstar Family of Funds
MERCANTILE MUTUAL FUNDS, INC.
(the "Company")
Investor Shares
of the
Balanced Portfolio, Equity Income Portfolio,
Equity Index Portfolio, Growth & Income Equity
Portfolio, Growth Equity Portfolio, Small Cap Equity
Portfolio, Small Cap Equity Index Portfolio and
International Equity Portfolio
Supplement dated September 26, 2000
to Prospectus dated March 31, 2000
Management of the International Equity Portfolio
------------------------------------------------
Clay Finlay Inc. ("Clay Finlay") serves as sub-adviser to the Company's
International Equity Portfolio (the "Portfolio"). Prior to 5:00 p.m. EDT on
September 25, 2000, Clay Finlay was an indirect subsidiary of United Asset
Management Corporation ("UAM"). At 5:00 p.m. EDT on September 25, 2000, Old
Mutual plc ("Old Mutual"), a public limited company based in the United Kingdom,
acquired over 90% of the outstanding stock of UAM pursuant to a tender offer, as
a result of which Clay Finlay is now an indirect subsidiary of Old Mutual. This
transaction constituted an assignment of, and automatically terminated, the
existing Sub-Advisory Agreement between Firstar Investment Research & Management
Company, LLC ("FIRMCO") and Clay Finlay with respect to the Portfolio. On
September 25, 2000, FIRMCO and Clay Finlay entered into an Interim Sub-Advisory
Agreement with respect to the Portfolio, which had been approved by the Board of
Directors of the Company at a meeting held on August 2, 2000. This action was
in accordance with the terms and conditions of Rule 15a-4 under the Investment
Company Act of 1940, as amended. Under Rule 15a-4, an adviser (or sub-adviser)
can serve pursuant to an interim advisory (or sub-advisory) agreement for up to
150 days while a fund seeks shareholder approval of a new investment advisory
(or sub-advisory agreement).
At a meeting held on July 11, 2000, the Board of Directors of the Company
approved a new Sub-Advisory Agreement between FIRMCO and Clay Finlay with
respect to the Portfolio. A Special Meeting of Shareholders of the Portfolio has
been scheduled for October 13, 2000 to consider and vote on the new Sub-Advisory
Agreement. Shareholders of record of the Portfolio as of the close of business
on August 28, 2000 are entitled to notice of, and to vote at, the Special
Meeting. The sub-advisory fees earned by Clay Finlay under the Interim
Sub-Advisory Agreement will be held in an interest-bearing escrow account at the
Fund's custodian, Firstar Bank, N.A., and will be paid to Clay Finlay if
shareholders of the Portfolio approve the new Sub-Advisory Agreement.
