<PAGE>
The Munder Funds
Supplement Dated September 28, 2000
to Prospectus Dated April 28, 2000
Class K Shares of:
Munder Institutional S&P 500 Index Equity Fund, Munder Institutional S&P MidCap
Index Equity Fund, Munder Institutional S&P SmallCap Index Equity Fund, Munder
Institutional Short Term Treasury Fund and Munder Institutional Money Market
Fund
FEE WAIVER FOR MUNDER INSTITUTIONAL MONEY MARKET FUND
Effective October 1, 2000, the advisor has agreed to reduce its management fees
for the Money Market Fund to 0.12% at least through September 30, 2001.
Accordingly, the Annual Fund Operating Expenses for the Money Market Fund in
the "Fees and Expenses" section in the prospectus is hereby deleted and
replaced with the following:
<TABLE>
<CAPTION>
Annual Fund Operating Expenses (expenses that are paid from Fund
assets) Money Market
as a % of net assets Fund
---------------------------------------------------------------- ------------
<S> <C>
Management Fees (1)................................................ .20%
Other Expenses
Shareholder Servicing Fee........................................ .25%
Other Operating Expenses (1)..................................... .18%
---
Total Other Expenses............................................. .43%
---
Total Annual Fund Operating Expenses(1)............................ .63%
===
</TABLE>
--------
(1) The advisor has contractually agreed to reduce the management fees for the
Money Market Fund to 0.12% at least through September 30, 2001. In
addition, the advisor has voluntarily agreed to reimburse operating
expenses to keep the Money Market Fund's Other Expenses at a specified
level. The advisor may eliminate all or part of the operating expense
reimbursement at any time. Because of the fee waiver and expense
reimbursement, the actual management fees, other operating expenses and
total annual fund operating expenses are expected to be: 0.12%, 0.00% and
0.37%, respectively, for the Money Market Fund.
SUPPPROINSTK92800
<PAGE>
The Munder Funds
Supplement Dated September 28, 2000
to Prospectus Dated April 28, 2000
Class Y Shares of:
Munder Institutional S&P 500 Index Equity Fund, Munder Institutional S&P MidCap
Index Equity Fund, Munder Institutional S&P SmallCap Index Equity Fund, Munder
Institutional Short Term Treasury Fund and Munder Institutional Money Market
Fund
FEE WAIVER FOR MUNDER INSTITUTIONAL MONEY MARKET FUND
Effective October 1, 2000, the advisor has agreed to reduce its management fees
for the Money Market Fund to 0.12% at least through September 30, 2001.
Accordingly, the Annual Fund Operating Expenses for the Money Market Fund in
the "Fees and Expenses" section in the prospectus is hereby deleted and
replaced with the following:
<TABLE>
<CAPTION>
Annual Fund Operating Expenses (expenses that are paid from Fund
assets) Money Market
as a % of net assets Fund
---------------------------------------------------------------- ------------
<S> <C>
Management Fees(1)............................................... .20%
Other Expenses(1)................................................ .18%
---
Total Annual Fund Operating Expenses(1).......................... .38%
===
</TABLE>
--------
(1) The advisor has contractually agreed to reduce the management fees for the
Money Market Fund to 0.12% at least through September 30, 2001. In
addition, the advisor has voluntarily agreed to reimburse operating
expenses to keep the Money Market Fund's Other Expenses at a specified
level. The advisor may eliminate all or part of the operating expense
reimbursement at any time. Because of the fee waiver and expense
reimbursement, the actual management fees, other operating expenses and
total annual fund operating expenses are expected to be: 0.12%, 0.00% and
0.12%, respectively, for the Money Market Fund.
SUPPPROINSTY92800
