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MFS(R) MID CAP VALUE FUND
Supplement to the Current Prospectus
The third paragraph under the caption "Principal Investment Policies" is revised
as follows:
Medium market capitalization companies are defined by the fund as
companies with market capitalizations equaling or exceeding $250 million but not
exceeding the top of the Russell Midcap TM Index range at the time of the fund's
investment. This Index is a widely recognized, unmanaged index of mid-cap common
stock prices. Companies whose market capitalizations fall below $250 million or
exceed the top of the Russell Midcap TM Index range after purchase continue to
be considered medium-capitalization companies for purposes of the fund's 65%
investment policy. As of July 9, 1999 the top of the Russell Midcap TM Index
range was $12.7 billion. The fund's investments may include securities traded in
the over-the-counter markets.
The date of this Supplement is July 16, 1999.
