SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549


                                    FORM 8-A

                For Registration of Certain Classes of Securities
                    Pursuant to Section 12(b) or 12(g) of the
                         Securities Exchange Act of 1934

                                SIS BANCORP, INC.
             (Exact Name of Registrant as Specified in its Charter)



               Massachusetts                          04-3303264
      (State or Other Jurisdiction                  (IRS Employer
            of Incorporation)                     Identification No.)

             1441 Main Street                             01102
        Springfield, Massachusetts                     (Zip Code)
      (Address of principal office)


If this Form relates to the               If this Form relates to the         
registration of a class of debt           registration of a class of debt     
securities and is effective upon          securities and is to become         
filing pusuant to General                 effective simultaneously with       
Instruction A(c)(1), please check         the effectiveness of a concurrent   
the following box. / /                    registration statement under the    
                                          Securities Act of 1993 pursuant     
                                          to General Instruction A(c)(2),     
                                          please check the following box. / / 



        Securities to be registered pursuant to Section 12(b)of the Act:


          Title of Each Class               Name of Each Exchange on Which
          to be so Registered               Each Class is to be Registered
                 None

        Securities to be registered pursuant to Section 12(g) of the Act:

                         Preferred Share Purchase Rights
                                (Title of Class)







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Item 1.  Description of Registrant's Securities to be Registered.

         On January 22, 1997, the Board of Directors of SIS Bancorp,  Inc. (the
"Company"),  declared a dividend  distribution  of one Preferred  Share Purchase
Right (a "Right") for each of the Company's  outstanding shares of common stock,
par value  $.01 per share  (the  "Common  Shares"),  to holders of record of the
Common Shares at the close of business on February 3, 1997. Each Right entitles
the registered  holder to purchase from the Company one one-hundredth of a share
of preferred  stock,  par value $.01 per share,  of the Company (the  "Preferred
Shares") or in certain circumstances,  to receive cash, property,  Common Shares
or other  securities  of the  Company,  at a Purchase  Price of $100.00  per one
one-hundredth of a Preferred Share,  subject to adjustment.  The description and
terms of the Rights are set forth in a Rights Agreement (the "Rights Agreement")
between the Company and  ChaseMellon  Shareholder  Services,  L.L.C.,  as Rights
Agent.

         Initially, the Rights will be attached to all certificates representing
the Common Shares and no separate Rights  Certificates will be distributed.  The
Rights will separate from the Common Shares and a  Distribution  Date will occur
upon the  earlier of (i) 10 business  days (or such later date as the  Company's
Board of Directors may determine before a Distribution  Date occurs) following a
public  announcement  by the  Company  that a person or group of  affiliated  or
associated  persons,  with  certain  exceptions  (an  "Acquiring  Person"),  has
acquired,  or has obtained the right to acquire  beneficial  ownership of 10% or
more of the outstanding  Common Shares (the date of such announcement  being the
"Share  Acquisition  Date") or (ii) 10 business  days (or such later date as the
Company's  Board of Directors may determine  before a Distribution  Date occurs)
following the commencement of a tender offer or exchange offer that would result
in a person becoming an Acquiring Person.

         Until the  Distribution  Date,  (i) the Rights will be evidenced by the
certificates  for Common Shares and will be transferred  with and only with such
Common  Share  certificates,  (ii)  Common  Share  certificates  will  contain a
notation incorporating the Rights Agreement by reference and (iii) the surrender
for  transfer  of any  certificates  for  Common  Shares  outstanding  will also
constitute  the  transfer  of the  Rights  associated  with  the  Common  Shares
represented by such certificates.

         The Rights are not  exercisable  until the  Distribution  Date and will
expire at the close of business on January 22, 2007, unless earlier redeemed or
exchanged by the Company as described below.

         As soon as practicable after the Distribution Date, Rights Certificates
will be mailed to  holders  of  record of the  Common  Shares as of the close of
business on the Distribution Date and, from and after the Distribution Date, the
separate Rights Certificates alone will represent the Rights.

         In the event (a "Flip-In  Event") a Person becomes an Acquiring  Person
(except pursuant to a tender or exchange offer for all outstanding Common Shares
at a price and on terms which a majority of the Company's  Outside Directors (as
defined in the Rights  Agreement)  determines to be fair to and otherwise in the
best  interests  of the Company and its  shareholders  (a "fair  offer")),  each
holder of a Right will  thereafter  have the right to receive,  upon exercise of
such Right, Common Shares (or, in certain circumstances, cash, property or other
securities of the Company)  having a Current Market Price (as defined the Rights
Agreement)  equal to two times the exercise price of the Right.  Notwithstanding






                                       -3-

the foregoing,  following the  occurrence of any Flip-In Event,  all Rights that
are, or (under certain  circumstances  specified in the Rights  Agreement) were,
beneficially  owned by any Acquiring Person (or by certain related parties) will
be null  and  void in the  circumstances  set  forth  in the  Rights  Agreement.
However,  Rights will not be exercisable following the occurrence of any Flip-In
Event until such time as the Rights are no longer  redeemable  by the Company as
set forth below.

         For example,  at an exercise price of $100.00 per Right, each Right not
owned by an Acquiring Person (or by certain related parties) following a Flip-In
Event would  entitle its holder to purchase  $200.00  worth of Common Shares (or
other  consideration,  as noted  above) for  $100.00.  Assuming  that the Common
Shares had a Current  Market  Price of $25.00 at such  time,  the holder of each
valid Right would be entitled to purchase 8 Common Shares for $100.00.

         In the event (a  "Flip-Over  Event")  that, at any time on or after the
Share  Acquisition  Date,  (i) the Company  shall take part in a merger or other
business combination  transaction (other than certain mergers that follow a fair
offer) and the  Company  shall not be the  surviving  entity or (ii) the Company
shall take part in a merger or other business  combination  transaction in which
the Common  Shares are changed or  exchanged  (other than  certain  mergers that
follow a fair  offer) or (iii) 50% or more of the  Company's  assets or  earning
power is sold or  transferred,  each  holder  of a Right  (except  Rights  which
previously have been voided, as set forth above) shall thereafter have the right
to receive,  upon exercise,  a number of shares of common stock of the acquiring
company  having a Current  Market Price equal to two times the exercise price of
the Right.

         The Purchase  Price payable and the number of Preferred  Shares (or the
amount of cash,  property or other  securities)  issuable  upon  exercise of the
Rights are subject to  adjustment  from time to time to prevent  dilution (i) in
the  event  of  a  share   dividend  on,  or  a   subdivision,   combination  or
reclassification  of, the  Preferred  Shares,  (ii) if holders of the  Preferred
Shares are granted certain rights or warrants to subscribe for Preferred  Shares
or convertible securities at less than the Current Market Price of the Preferred
Shares or (iii) upon the  distribution  to holders  of the  Preferred  Shares of
evidences of indebtedness or assets (excluding regular quarterly cash dividends)
or of subscription rights or warrants (other than those referred to above).

         With certain  exceptions,  no adjustment in the Purchase  Price will be
required  until  cumulative  adjustments  amount  to at lest 1% of the  Purchase
Price. The Company is not required to issue fractional Preferred Shares upon the
exercise  of any Right or  Rights  evidenced  hereby.  In lieu  thereof,  a cash
payment may be made, as provided in the Rights Agreement.

         At any time until 10  business  days  following  the Share  Acquisition
Date, the Company may redeem the Rights in whole, but not in part, at a price of
$.01 per Right, payable, at the option of the Company, in cash, Common Shares or
other  consideration  as the Board of Directors may determine.  Immediately upon
the  effectiveness  of the action of the Company's  Board of Directors  ordering
redemption  of the Rights,  the Rights will  terminate and the only right of the
holders of Rights will be to receive the $.01 per Right redemption price.

         Until a Right is exercised,  the holder thereof,  as such, will have no
rights as a shareholder of the Company, including, without limitation, the right
to vote or to receive  dividends.  While the distribution of the Rights will not
be taxable to shareholders or to the Company,  shareholders may,  depending upon
the circumstances, recognize taxable income in the event that the Rights become





                                       -4-


exercisable for Common Shares (or cash,  property,  or other  securities) of the
Company or for common stock of the acquiring company as set forth above.

         The terms of the Rights, other than key financial terms and the date on
which the Rights expire, may be amended by the Board of Directors of the Company
prior  to the  Distribution  Date.  Thereafter,  the  provisions  of the  Rights
Agreement  may be  amended by the Board of  Directors  only in order to cure any
ambiguity,  defect or  inconsistency,  to make  changes  which do not  adversely
affect the  interests  of  holders of Rights  (excluding  the  interests  of any
Acquiring  Person and certain other  related  parties) or to shorten or lengthen
any time period under the Rights Agreement; provided, however, that no amendment
to lengthen the time period  governing  redemption shall be made at such time as
the Rights are not redeemable.

         This summary  description of the Rights does not purport to be complete
and is qualified in its entirety by referenced to the Rights  Agreement filed as
Exhibit  4.1  hereto.  Capitalized  terms used and not  defined  herein have the
meanings set forth in the Rights Agreement.

Item 2.  Exhibits.

         The  following  exhibits  are  filed  as a part  of  this  Registration
Statement.

Exhibit Number             Description

         4.1      Rights  Agreement  dated as of January 22, 1997  between SIS
                  Bancorp, Inc. and ChaseMellon Shareholder Services, L.L.C., as
                  Rights Agent.

         4.2      Terms  of  Series  A  Junior  Participating  Preferred  Stock,
                  included as Exhibit A to Rights Agreement.

         4.3      Summary  of  Rights  to  Purchase  Shares  of  Series A Junior
                  Participating Preferred Stock, included as Exhibit B to Rights
                  Agreement.

         4.4      Form of Rights  Certificate,  included  as Exhibit C to Rights
                  Agreement.







                                       -5-


                                   Signatures

         Pursuant to the  requirements of Section 12 of the Securities  Exchange
Act of 1934, the Registrant has caused this registration  statement to be signed
on its behalf by the undersigned, thereunto duly authorized.



                                            SIS BANCORP, INC.



Date:  January 23, 1997                     By:  /s/ F. William Marshall, Jr.
                                                     F. William Marshall, Jr.
                                                     President