July 24, 1997
PIONEER MID-CAP FUND
SUPPLEMENT TO PROSPECTUS
DATED JANUARY 28, 1998
Effective July 24, 1998, the Fund will implement certain changes in its
non-fundamental investment policies. The following information supplements the
corresponding sections in the Prospectus. Please consult the Prospectus for the
full text of the revised sections.
COVER PAGE
The first four sentences of the second paragraph on the cover page are
revised as follows:
In seeking to achieve its investment objective, the Fund will invest at
least 65% of its total assets in common stocks and common stock equivalents
(such as convertible bonds and preferred stock) of companies considered to be
mid-capitalization companies ("Mid-Cap Companies"). Mid-Cap Companies include
companies with market capitalizations within the range of market capitalizations
reflected in Standard & Poor's MidCap 400 Index (the "Index"). As of July 1998,
the market capitalization range of companies comprising the Index was $330
million to $22.92 billion. The weighted average market capitalization of the
securities held in the Fund's portfolio may range from $1 billion to $10
billion.
III. INVESTMENT OBJECTIVE AND POLICIES
The first four sentences of the third paragraph are replaced with the
following:
Under normal circumstances, at least 65% of the Fund's total assets are
invested in common stocks of Mid-Cap Companies. Mid-Cap Companies include
companies with market capitalizations at the time of investment within the range
of market capitalizations reflected in the Index. As of July 1998, the market
capitalization range of companies comprising the Index was $330 million to
$22.92 billion. The weighted average market capitalization of the securities
held in the Fund's portfolio may range from $1 billion to $10 billion.
0798-5530
(C) Pioneer Funds Distributor, Inc.
