<PAGE>
BARR ROSENBERG SERIES TRUST
Supplement dated September 26, 2000
to
Prospectus dated July 31, 2000
This supplement is provided to update, and should be read in conjunction
with, the information provided in the Prospectus.
The AXA Rosenberg Multi-Strategy Market Neutral Fund will become operational
on September 29, 2000. Accordingly, as noted in the Prospectus, the AXA
Rosenberg Double Alpha Market Fund will cease investing in the AXA Rosenberg
Value Market Neutral Fund and begin investing in the AXA Rosenberg
Multi-Strategy Market Neutral Fund as of that date.
INVESTMENT OBJECTIVE AND PRINCIPAL INVESTMENT STRATEGIES
Beginning September 29, 2000, investors should consider the investment
objective, principal investment strategies and principal risks of the AXA
Rosenberg Multi-Strategy Market Neutral Fund, as described in the Prospectus,
when deciding whether to invest in the AXA Rosenberg Double Alpha Market Fund.
The subsections entitled "AXA Rosenberg Double Alpha Market Fund" in the
Prospectus sections entitled "Risk/Return Summary" and "Investment Objectives
and Principal Investment Strategies" are hereby amended accordingly.
PRINCIPAL RISKS
Because it will cease investing in the AXA Rosenberg Value Market Neutral
Fund as of September 29, 2000, the principal risks for the AXA Rosenberg Double
Alpha Market Fund will no longer include Small and Mid-Sized Company Risk after
that date. The Prospectus section entitled "Principal Risks" is hereby amended
accordingly.
FEES AND EXPENSES
GENERAL
Because, as described in the Prospectus, the Adviser has undertaken to waive
its management fee and/ or bear certain expenses for each Fund at least through
the end of the current fiscal year, each table entitled "Example", including the
"Example" table for the AXA Rosenberg Double Alpha Market Fund set forth below,
in the Prospectus section entitled "Fees and Expenses" assumes that the relevant
Fund would pay the Net Expenses (after Fee Waiver and/or Expense Reimbursement)
during the first year following a $10,000 investment and the Total Annual Fund
Operating Expenses (before Fee Waiver and/or Expense Reimbursement) thereafter.
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AXA ROSENBERG DOUBLE ALPHA MARKET FUND
The subsection entitled "AXA Rosenberg Double Alpha Market Fund" in the
Prospectus section entitled "Fees and Expenses" is hereby amended in its
entirety, as of September 29, 2000, to read as follows:
SHAREHOLDER FEES (paid directly from your investment):
<TABLE>
<CAPTION>
INSTITUTIONAL INVESTOR
------------- --------
<S> <C> <C>
Maximum Sales Charge (Load) Imposed on Purchases............ None None
Maximum Deferred Sales Charge (Load)........................ None None
Maximum Sales Charge (Load) Imposed on Reinvested
Dividends................................................. None None
Redemption Fee.............................................. None None
Exchange Fee................................................ None None
</TABLE>
ANNUAL FUND OPERATING EXPENSES (expenses that are deducted from Fund assets)
<TABLE>
<CAPTION>
INSTITUTIONAL INVESTOR
------------- --------
<S> <C> <C>
Management Fees............................................. 0.10% 0.10%
Distribution and Shareholder Service (12b-1) Fees........... None 0.25%
Other Expenses (a)
Dividend Expenses on Securities Sold Short................ 1.00% 1.00%
Remainder of Other Expenses............................... 3.39% 3.54%(b)
Total....................................................... 4.39% 4.54%
Total Annual Fund Operating Expenses........................ 4.49% 4.89%
Fee Waiver and/or Expense Reimbursement (c)................. 1.64% 1.64%
Net Expenses................................................ 2.85% 3.25%
</TABLE>
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<TABLE>
<C> <S>
(a) Because the AXA Rosenberg Double Alpha Market Fund invests
in the AXA Rosenberg Multi- Strategy Market Neutral Fund,
its "Other Expenses" include the net expenses of that Fund,
including that Fund's net management fees after waiver and
expenses from dividends on securities sold short.
(b) The Trustees have authorized the payment of up to 0.15% of
the Fund's average daily net assets attributable to Investor
Shares for subtransfer and subaccounting service in
connection with such shares.
(c) The Adviser has contractually undertaken to waive its
management fee and bear certain expenses (exclusive of
nonrecurring account fees, extraordinary expenses and
dividends and interest paid on securities sold short) until
further notice (and in any event at least until 3/31/01).
Any amounts waived or reimbursed in a particular fiscal year
will be subject to repayment by the Fund to the Adviser to
the extent that from time to time through the next two
fiscal years the repayment will not cause the Fund's
expenses to exceed the stated limit during the respective
year.
</TABLE>
EXAMPLE
This example is intended to help you compare the cost of investing in the
Fund with the cost of investing in other mutual funds.
The example assumes that you invest $10,000 in the Fund for the time periods
indicated and then redeem all of your shares at the end of those periods. The
example also assumes that your investment earns a 5% return each year and that
the Fund's operating expenses remain the same as those shown above. Your actual
costs may be higher or lower. Based on these assumptions, your costs would be:
<TABLE>
<CAPTION>
CLASS 1 YEAR 3 YEARS 5 YEARS 10 YEARS
----- -------- -------- -------- --------
<S> <C> <C> <C> <C>
Institutional............................................... $288 $1,210 $2,141 $4,512
Investor.................................................... $328 $1,324 $2,322 $4,828
</TABLE>
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