April 17, 2003

SUPPLEMENT TO THE MARCH 1, 2003 CLASS A, B, C PROSPECTUS, CLASS R PROSPECTUS AND
                CLASS Y PROSPECTUS FOR PIONEER MID CAP VALUE FUND

The following supplements the corresponding section of the prospectus. Please
refer to the prospectus for the full text of the supplemented section.

MANAGEMENT

INVESTMENT ADVISER

Pioneer has received an order from the Securities and Exchange Commission that
permits Pioneer, subject to the approval of the fund's Board of Trustees, to
hire and terminate a subadviser or to materially modify an existing subadvisory
contract for the fund without shareholder approval. Pioneer retains the ultimate
responsibility to oversee and recommend the hiring, termination and replacement
of any subadviser. Currently, Pioneer does not intend to use a subadviser in
connection with the fund, but will be able to do so in the future with the
approval of the fund's trustees.

MANAGEMENT FEE
The fund pays Pioneer a fee for managing the fund and to cover the cost of
providing certain services to the fund.

Pioneer's fee varies based on:
o    The fund's assets; Pioneer earns an annual basic fee equal to 0.70% of the
     fund's average daily net assets up to $500 million, 0.65% of the next $500
     million and 0.625% on assets over $1 billion.
o    Effective May 1, 2003, the investment performance of the fund compared to
     the Russell Midcap Value Index. The performance comparison is made for a
     rolling 36-month period. For periods prior to May 1, 2003, the performance
     comparison will be made to the Lipper Growth Fund Index.



                                                                   13612-00-0403
                                        (C) 2003 Pioneer Funds Distributor, Inc.
                                                                     Member SIPC