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                           VANGUARD EXPLORER(TM) FUND
                 SUPPLEMENT TO THE PROSPECTUS DATED MAY 30, 2000

Effective  August 1,  2000,  the Fund's  benchmark  will  change  from the Small
Company  Growth  Fund Stock  Index to the Russell  2000  Growth  Index.  The new
benchmark will assist investors in evaluating the Fund's  performance,  and will
be  used  to  calculate  performance  fees  paid  to  four  of the  Fund's  five
advisers--Granahan  Investment Management,  Inc., Wellington Management Company,
LLP, Chartwell Investment Partners,  and Grantham,  Mayo, Van Otterloo & Co. LLC
(Vanguard Quantitative Equity Group provides its services on an at-cost basis).
     While  the Small  Company  Growth  Fund  Stock  Index  has been a  suitable
benchmark  for  the  Fund,  the  Russell  2000  Growth  Index  is a more  widely
recognized  measure of the performance of small-cap  growth stocks.  Because the
two indexes' characteristics are broadly similar,  however, the change will have
little  effect on the Fund's  investments,  strategies,  or risk  level,  and no
effect on its policies.



(C)2000 The Vanguard Group, Inc. All rights reserved.               PS24N 082000
Vanguard Marketing Corporation, Distributor.