MFS SUN LIFE SERIES TRUST, 497J, 1997-05-02

MFS SUN LIFE SERIES TRUST
497J, 1997-05-02

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                            MFS/SUN LIFE SERIES TRUST
               500 Boylston Street Boston Massachusetts 02116-3741
                                  617 954 5000




                                            May 2, 1997



VIA EDGAR

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

         Re:  MFS/Sun Life Series Trust (the "Trust") (File No.  2-83616)

Ladies and Gentlemen:

         Pursuant to Rule 497(j) under the  Securities  Act of 1933, as amended,
please accept this letter as certification  that the Prospectus and Statement of
Additional  Information  for the Trust do not  differ  from those  contained  in
Post-Effective  Amendment No. 20 (the  "Amendment") to the Trust's  Registration
Statement on Form N-1A.  The  Amendment  was filed  electronically  on April 29,
1997.

         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 R. BORDEWICK, JR.
                                            James R. Bordewick, Jr.
                                            Assistant Secretary

JRB/bjn