8-K

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549


              -----------------------------------------------------



                                    FORM 8-K

                                 CURRENT REPORT
                     PURSUANT TO SECTION 13 OR 15(d) OF THE
                         SECURITIES EXCHANGE ACT OF 1934




                Date of Report (Date of earliest event reported):
                     December 31, 1997 (December 17, 1997)




                                SIS Bancorp, Inc.
               (Exact name of registrant as specified in charter)




      Massachusetts                   000-20809                   04-3303264
(State or other jurisdiction    (Commission file number)       (IRS employer 
     of incorporation)                                       identification no.)

   1441 Main Street, Springfield, MA                                01102
(Address of principal executive offices)                          (Zip code)

                                 (413) 748-8000
               Registrant's telephone number, including area code




Item 2. ACQUISITION OR DISPOSITION OF ASSETS

         On December 17, 1997, SIS Bancorp,  Inc.  ("SIS")  completed its merger
(the "Merger") with  Glastonbury  Bank & Trust Company  ("GBT"),  pursuant to an
Agreement  and Plan of  Reorganization  dated as of August 18, 1997 (the "Merger
Agreement")  by and  between SIS and GBT.  In  accordance  with the terms of the
Merger  Agreement,  a wholly owned  subsidiary  of SIS merged with and into GBT,
which then became a wholly  owned  subsidiary  of SIS.  Each share of GBT common
stock, par value $2.50 per share,  outstanding  immediately  prior to the Merger
was converted  into the right to receive  74/100ths  (0.74) of a share of common
stock of SIS, par value $.01 per share.

         The Merger  constitutes a tax-free  reorganization  and no gain or loss
will be recognized  by SIS or GBT as a result of the Merger.  The Merger will be
accounted for as a "pooling of interests" transaction.

         Certain  additional  information  regarding  the Merger is contained in
SIS's press release  dated  December 18, 1997, a copy of which is included as an
exhibit hereto and incorporated herein.

Item 7. FINANCIAL STATEMENTS AND EXHIBITS

(c)      Exhibits.

         99.1     Press Release of SIS, dated December 18, 1997








                                   SIGNATURES

         Pursuant to the  requirements  of the Securities  Exchange Act of 1934,
SIS Bancorp,  Inc. has duly caused this report to be signed on its behalf by the
undersigned hereunto duly authorized.


                                SIS BANCORP, INC.


Date: December 31, 1997        By: /s/ John F. Treanor
                                   Name: John F. Treanor
                                   Title:  Executive Vice President, Chief 
                                             Financial Officer and Treasurer

EX-99.1

                                                                   Exhibit 99.1

         P R E S S                                               SIS Bancorp
    R E L E A S E



                              FOR IMMEDIATE RELEASE

Date: December 18, 1997                   Contact:  Ting Chang, Vice President
                                                            Investor Relations
                                                                (413) 748-8271

            SIS BANCORP COMPLETES MERGER OF GLASTONBURY BANK & TRUST

Springfield,   Massachusetts,  December  18,  1997--SIS  Bancorp,  Inc.  ("SIS")
(NASDAQ:  SISB) and  Glastonbury  Bank & Trust Company  ("GBT")  (NASDAQ:  GLBT)
announced today that,  having received all necessary  regulatory and stockholder
approvals, the merger of GBT with SIS has been completed. The merger resulted in
GBT becoming a wholly owned banking subsidiary of SIS.

"We are pleased to have been able to  complete  this  transaction  as planned by
year end," said F. William Marshall,  Jr., president and chief executive officer
of SIS Bancorp.  "I am grateful for the efforts of the Board of  Directors,  the
shareholders,  and the employees of SIS and GBT that have made this possible. As
we embark upon a new  beginning,  we will continue to focus on those  activities
that have  brought us success to date.  We look  forward to the new year and the
opportunity to realize the potential of our combined companies," said Marshall.

As a result of the merger,  SIS is now a financial  institution of approximately
$1.7  billion  in total  assets.  SIS is the  holding  company  for  Springfield
Institution   for  Savings,   headquartered   in   Springfield,   MA,  and  GBT,
headquartered  in  Glastonbury,  CT.  These  subsidiaries  operate a total of 34
banking offices in central Connecticut and western Massachusetts.

The merger was completed by the exchange of approximately  1.4 million shares of
SIS common stock for all  outstanding  GBT common  stock.  Based on a twenty-day
average  closing bid price of SIS common stock  through  December  10, 1997,  of
$34.63,   GBT  shareholders   would  be  entitled  to  receive  stock  equal  to
approximately  $25.63  for each share of GBT  common  stock and the  transaction
would be valued at approximately $46.9 million.

After the issuance of the additional shares of common stock for the merger,  SIS
Bancorp will have  approximately  6.9 million shares  outstanding.  These shares
will  continue  to be traded on the  NASDAQ  National  Market  System  under the
current symbol of SISB.

Any  questions  pertaining  to this  release may be forwarded to Ms. Ting Chang,
vice president Investor Relations, at (413) 748-8271.