<PAGE>
Filed Pursuant to Rule 497(e)
Registration No.: 33-63685
SUPPLEMENT TO THE STATEMENT OF ADDITIONAL INFORMATION OF
MORGAN STANLEY DEAN WITTER MID-CAP EQUITY TRUST
DATED JANUARY 28, 2000
The third paragraph of the section entitled "V. Investment Management and
Other Services -- A. Investment Manager and Sub-Advisor" in the above Statement
of Additional Information is revised to reflect that, effective May 1, 2000,
the Trustees of the Fund have amended the Fund's Investment Management
Agreement to reduce the compensation received by the Investment Manager under
the Agreement for assets exceeding $2 billion, so that the compensation under
the Agreement is calculated daily by applying the following annual rates to the
Fund's net assets determined as of the close of each business day: 0.75% of the
portion of daily net assets not exceeding $500 million; 0.725% of the next $1.5
billion; 0.70% of the next $1 billion; and 0.675% of the portion of daily net
assets exceeding $3 billion.
May 15, 2000