MASSACHUSETTS FINANCIAL SERVICES COMPANY
              500 Boylston Street, Boston, Massachusetts 02116-3741
                                 617 - 954-5000




                                        March 2, 2007

VIA EDGAR
United States Securities & Exchange Commission
100 F Street, N.E.
Washington, DC  20549

  Re:  Request for  Withdrawal  of  Registration  Statement  on Form N-1A for
       MFS(R) Series Trust I File No. 33-7638; Accession No.0000950156-07-000058

Ladies and Gentlemen:

     Pursuant to Rule 477 under the Securities Act of 1933, the MFS Series Trust
I ("Registrant"), on behalf of MFS Cash Reserve Fund, respectfully requests that
the  Securities  and  Exchange  Commission  (the  "Commission")  consent  to the
withdrawal of the above  captioned Form N-1A  Registration  Statement  (File No.
33-7638)  filed  with the  Commission  at  14:49 PM on  January  29,  2007  (the
"Registration Statement").

     This request for withdrawal is being made because the  Registrant  will not
be  registering  Class I and Class R shares for the series.  No securities  were
sold in connection with the Registration Statement.

     Registrant  respectfully  submits  that a  withdrawal  of the  Registration
Statement is consistent with the public interest and the protection of investors
in light of the  circumstances  described  above.  Any questions  regarding this
matter may be directed to Jessica Rung at  617-954-6149  or the  undersigned  at
617-954-4340.

                                        Sincerely,



                                        SUSAN A. PEREIRA
                                        Susan A. Pereira
                                        Senior Counsel