MFS SERIES TRUST XI, 497, 1999-04-22

MFS SERIES TRUST XI
497, 1999-04-22

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                               VERTEX ALL CAP FUND
                            VERTEX U.S. ALL CAP FUND
                             VERTEX CONTRARIAN FUND

                            SUPPLEMENT TO PROSPECTUS




         The Funds'  prospectus  states  that MFS  intends to waive its right to
receive management fees from each Fund until April 30, 1999, and that commencing
May 1, 1999, each Fund will pay management fees to MFS.

         MFS will  continue to waive its right to receive  management  fees from
each Fund on and after May 1, 1999.  This waiver will continue for an indefinite
period and may be terminated at any time at MFS' discretion.





                  The date of the Supplement is April 16, 1999