MFS SUN LIFE SERIES TRUST, 497J, 2000-05-01

MFS SUN LIFE SERIES TRUST
497J, 2000-05-01

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                    MASSACHUSETTS FINANCIAL SERVICES COMPANY
             500 BOYLSTON STREET, BOSTON, MASSACHUSETTS 02116-3741
                                  617-954-5000




                                        May 1, 2000



VIA EDGAR

Securities and Exchange Commission
Judiciary Plaza
450 Fifth Street, NW
Washington, DC  20549

         Re:   MFS(R)/Sun Life Series Trust (the "Trust") (File Nos. 2-83616 and
               811-3732)

Ladies and Gentlemen:

         Pursuant to Rule 497(j) under the  Securities  Act of 1933, as amended,
please  accept  this  letter on behalf  of the Trust as  certification  that the
Prospectus and Statement of Additional  Information  for the Trust do not differ
from those contained in Post-Effective Amendment No. 25 (the "Amendment") to the
Trust's   Registration   Statement  on  Form  N-1A.   The  Amendment  was  filed
electronically on April 28, 2000.

         Please call the undersigned or Karen M. Ray at (617) 954-5801 or(800)
343-2829 with any questions you may have.

                                        Very truly yours,



                                        JAMES F. DESMARAIS
                                        James F. DesMarais
                                        Assistant General Counsel

JFD/bjn