<PAGE>
EXHIBIT NO. 99.1(o)
MFS SERIES TRUST I
CERTIFICATION OF AMENDMENT
TO THE DECLARATION OF TRUST
ESTABLISHMENT AND DESIGNATION
OF CLASSES
Pursuant to Section 6.9 of the Amended and Restated Declaration of
Trust dated January 6, 1995, as amended (the "Declaration"), of MFS Series Trust
I, a business trust organized under the laws of The Commonwealth of
Massachusetts (the "Trust"), the undersigned Trustees of the Trust, being a
majority of the Trustees of the Trust, do hereby divide the shares of MFS
Managed Sectors Fund, a series of the Trust, to create an additional class of
shares, within the meaning of Section 6.10, as follows:
1. The additional class of shares is designated "Class C Shares";
2. Class C Shares shall be entitled to all the rights and preferences
accorded to shares under the Declaration;
3. The purchase price of Class C Shares, the method of determination
of the net asset value of Class C Shares, the price, terms and
manner of redemption of Class C Shares, and the relative dividend
rights of holders of Class C Shares shall be established by the
Trustees of the Trust in accordance with the Declaration and shall
be set forth in the current prospectus and statement of additional
information of the Trust or any series thereof, as amended from
time to time, contained in the Trust's registration statement under
the Securities Act of 1933, as amended;
4. Class C Shares shall vote together as a single class except that
Shares of a class may vote separately on matters affecting only
that class and Shares of a class not affected by a matter will not
vote on that matter; and
5. A class of Shares of any series of the Trust may be terminated by
the Trustees by written notice to the Shareholders of the class.
<PAGE>
IN WITNESS WHEREOF, a majority of the Trustees of the Trust have
executed this amendment, in one or more counterparts, all constituting a single
instrument, as an instrument under seal in The Commonwealth of Massachusetts, as
of this 31st day of May, 2000 and further certify, as provided by the provisions
of Section 9.3(d) of the Declaration, that this amendment was duly adopted by
the undersigned in accordance with the second sentence of Section 9.3(a) of the
Declaration.
WALTER E. ROBB, III
---------------------------- ----------------------------
Richard B. Bailey Walter E. Robb, III
63 Atlantic Avenue 35 Farm Road
Boston, MA 02110 Sherborn, MA 01770
MARSHALL N. COHAN ARNOLD D. SCOTT
---------------------------- ----------------------------
Marshall N. Cohan Arnold D. Scott
2524 Bedford Mews Drive 20 Rowes Wharf
Wellington, FL 33414 Boston, MA 02110
LAWRENCE H. COHN JEFFREY L.SHAMES
---------------------------- ----------------------------
Lawrence H. Cohn Jeffrey L. Shames
45 Singletree Road 38 Lake Avenue
Chestnut Hill, MA 02167 Newton, MA 02459
SIR J. DAVID GIBBONS J. DALE SHERRATT
---------------------------- ----------------------------
Sir J. David Gibbons J. Dale Sherratt
"Leeward" 86 Farm Road
5 Leeside Drive Sherborn, MA 01770
"Point Shares"
Pembroke, Bermuda HM 05
WARD SMITH
----------------------------
ABBY M. O'NEILL Ward Smith
---------------------------- 36080 Shaker Blvd
Abby M. O'Neill Hunting Valley, OH 44022
200 Sunset Road
Oyster Bay, NY 11771
