As filed with the Securities and Exchange Commission on May 8, 1998
                                             Registration No. 333-

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                         -------------------------------

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                                SIS BANCORP, INC.
             (Exact name of Registrant as Specified in Its Charter)

          Massachusetts                          04-3303264
  (State or other jurisdiction of        (I.R.S. Employer  Identification No.)
  incorporation or organization)

                                1441 Main Street
                        Springfield, Massachusetts 01102
                    (Address of Principal Executive Offices)

                       SIS Bancorp, Inc. Stock Option Plan
                  (as amended and restated as of March 1, 1998)
                            (Full Title of the Plan)

                             MICHAEL E. TUCKER, ESQ.
                    Senior Vice President and General Counsel
                                SIS Bancorp, Inc.
                                1441 Main Street
                        Springfield, Massachusetts 01102
                     (Name and Address of Agent For Service)

                                  (413)748-8000
          (Telephone number, including area code, of agent for service)

                                    Copy to:
                             STEPHEN J. COUKOS, ESQ.
                            Sullivan & Worcester LLP
                             One Post Office Square
                           Boston, Massachusetts 02109
<TABLE>
<CAPTION>
                                                   CALCULATION OF REGISTRATION FEE

                                                                  Proposed Maximum          Proposed Maximum
                                            Amount to be         Offering Price Per        Aggregate Offering          Amount of
  Title of Securities to be Registered       Registered                Share                     Price             Registration Fee
<S>                                        <C>                       <C>                  <C>                        <C>   
Common Stock, $.01 par value                340,000 (1)               $42.50 (2)           $14,450,000.00 (2)         $4,262.75
<FN>

(1) Represents the additional  number of shares of Common Stock authorized  under the Stock Option Plan, as amended and restated.  A
total number of 806,250  additional  shares authorized under the Stock Option Plan were previously  registered  pursuant to Form S-8
Registration  Statement No. 333-11443.  See also "Explanatory Note" below. Also includes an indeterminate number of securities which
may be issuable by reason of a reorganization,  recapitalization, exchange of shares, stock split, combination of shares or dividend
payable in shares of Common Stock or other securities, as provided under the plans.

(2) Pursuant to Rule 457(h) the offering price is calculated based upon the average of the bid and asked prices of the Common Stock
as reported on the National Association of Securities Dealers Automated Quotation, National Market System on May 5, 1998.
</FN>
</TABLE>
<PAGE>
                                EXPLANATORY NOTE

         This Registration  Statement is filed pursuant to General Instruction E
of Form S-8. A Form S-8 Registration  Statement,  No. 333-11443,  was previously
filed on September  5, 1996 to register a total of 868,650  shares of the common
stock, par value $0.01 per share (the "Common Stock"), of SIS Bancorp, Inc. (the
"Company"),  of which 806,250 shares were  authorized  for issuance  pursuant to
options  granted or to be granted  under the Company's  Director and  Management
Stock Option Plans (the "Prior  Plans").  On February  18, 1998,  the  Company's
Board of Directors  approved  the  Company's  Stock Option Plan,  as amended and
restated (the "Current  Plan"),  which,  among other changes to the Prior Plans,
consolidated  the Prior  Plans into the  Current  Plan and  increased  the total
number of shares of Common Stock previously  authorized under the Prior Plans by
340,000 shares.  The Current Plan was approved by the Company's  stockholders on
May 7, 1998. A total of  1,146,250  shares of Common  Stock are  authorized  for
issuance  pursuant to options that may be granted under the Current Plan,  which
includes all options previously granted under the Prior Plans.

         This Registration  Statement,  in accordance with General Instruction E
of Form S-8,  incorporates  by  reference  the  contents  of the prior  Form S-8
Registration  Statement,  No.  333-11443,  referenced  above.  This Registration
Statement  also  contains  a  Prospectus,   prepared  in  accordance   with  the
requirements  of Part I of Form S-3 (in accordance with Section C of the General
Instructions  to Form S-8),  which covers  re-offers and re-sales by the Selling
Shareholders  listed in the Prospectus of shares of the Common Stock that may be
either issued directly to certain directors and/or executive  officers under the
Company's  Director and Management  Restricted  Stock Plans or issued to certain
directors  and/or  executive  officers  pursuant  to their  exercise  of options
granted under the Current Plan, including options granted under the Prior Plans.

<PAGE>
Prospectus       
                                 618,600 Shares

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

                                SIS BANCORP, INC.

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

                                  COMMON STOCK
                           (Par Value $.01 Per Share)
                            -------------------------


         This  Prospectus  is being used in connection  with the offering,  from
time to time,  by  certain  shareholders  (the  "Selling  Shareholders")  of SIS
Bancorp, Inc. (the "Company"),  of up to 618,600 shares (the "Shares") of common
stock,  par value $.01 per share (the "Common  Stock"),  of the  Company,  which
either have been  acquired by certain  directors  and  executives of the Company
under the SIS Bancorp,  Inc.  Director and Management  Restricted Stock Plans or
may be acquired  pursuant to the exercise of options (the "Options")  granted to
certain  directors and  executives  of the Company  under the SIS Bancorp,  Inc.
Stock  Option  Plan,  as amended and  restated as of March 1, 1998 (the  "Option
Plan"),  which includes  Options  granted under the Company's prior Director and
Management  Stock Option Plans. The Company will not receive any of the proceeds
from the sale of the Shares by the Selling Shareholders.

         The Shares may be sold from time to time by the Selling Shareholders or
by pledgees, donees, transferees or other successors in interest. Such sales may
be made on the National  Association of Securities Dealers Automated  Quotation,
National  Market  System  ("NMS") at prices and at terms then  prevailing  or at
prices related to the then current market price, or in negotiated  transactions.
All discounts,  commissions or fees incurred in connection  with the sale of the
Shares  offered  hereby  will  be  paid by the  Selling  Shareholders  or by the
purchasers of the Shares,  except that the expenses of preparing and filing this
Prospectus  and the  related  Registration  Statement  with the  Securities  and
Exchange  Commission  (the  "Commission"),  and of registering or qualifying the
Shares will be paid by the Company.

         The Selling  Shareholders  and any broker  executing  selling orders on
behalf of the Selling  Shareholders may be deemed to be an "underwriter"  within
the meaning of the Securities Act of 1933, as amended (the "Securities Act"), in
which event any discounts,  concessions,  or commissions received by such broker
may be deemed to be underwriting commissions under the Securities Act.

         The  Common  Stock is listed on the NMS.  On May 5, 1998,  the  closing
price of the Common Stock on the NMS was $42.625 per share.

  THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES AND
   EXCHANGE COMMISSION, THE FEDERAL DEPOSIT INSURANCE CORPORATION OR ANY STATE
    SECURITIES COMMISSION, NOR HAS THE COMMISSION, CORPORATION, OR ANY STATE
 SECURITIES COMMISSION PASSED UPON THE ACCURACY OR ADEQUACY OF THIS PROSPECTUS.
            ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

 THE SHARES OF COMMON STOCK OFFERED BY THIS PROSPECTUS ARE NOT SAVINGS ACCOUNTS
  OR DEPOSITS AND ARE NOT INSURED BY THE FEDERAL DEPOSIT INSURANCE CORPORATION,
  THE BANK INSURANCE FUND, THE SAVINGS ASSOCIATION INSURANCE FUND OR ANY OTHER
    GOVERNMENTAL AGENCY, AND INVOLVE INVESTMENT RISK, INCLUDING THE POSSIBLE
                               LOSS OF PRINCIPAL.

                  The date of this Prospectus is May 8, 1998.
<PAGE>
         No person has been  authorized to give any  information  or to make any
representation  not contained in this  Prospectus,  and, if given or made,  such
information or representation  must not be relied upon as having been authorized
by the  Company.  This  Prospectus  does  not  constitute  an offer to sell or a
solicitation  of an offer to buy any  securities  other  than the  Common  Stock
offered by this  Prospectus or an offer to sell or a solicitation of an offer to
buy such Common Stock in any  jurisdiction  to any person to whom it is unlawful
to make such offer or solicitation in such jurisdiction. Neither the delivery of
this  Prospectus nor any sale made  hereunder  shall,  under any  circumstances,
create  any  implication  that  there has been no change in the  affairs  of the
Company or that the  information  herein is correct as of any time subsequent to
the date hereof.

                                TABLE OF CONTENTS

Section                                                                    Page

Available Information ..................................................     3

Incorporation of Certain Documents by Reference ........................     3

The Company ............................................................     4

Selling Shareholders ...................................................     4

Plan of Distribution ...................................................     6

Indemnification ........................................................     6

Experts ................................................................     7

Legal Matters ..........................................................     7


                                        2

<PAGE>
                              AVAILABLE INFORMATION

         The  Company  is  subject  to  the  informational  requirements  of the
Securities  Exchange  Act of 1934,  as amended  (the  "Exchange  Act"),  and, in
accordance  therewith,  files reports,  proxy statements,  and other information
with the Commission.  Such reports, proxy statements,  and other information can
be inspected  and copied at the public  reference  facilities  maintained by the
Commission  at 450  Fifth  Street,  N.W.,  Washington,  D.C.  20549,  and at the
following  Regional Offices:  the Northeast  Regional Office,  Seven World Trade
Center,  Suite 1300, New York, New York 10048,  and the Midwest Regional Office,
Citicorp  Center,  500  West  Madison  Street,  Suite  1400,  Chicago,  Illinois
60661-2511.  Copies of such material can be obtained by written request from the
Public  Reference  Section  of  the  Commission  at  450  Fifth  Street,   N.W.,
Washington,  D.C. 20549. The Company files  electronically  with the Commission.
The Commisssion maintains a World Wide Web site (located at  http://www.sec.gov)
that contains  reports,  proxy and information  statements and other information
regarding registrants that file electronically with the Commission.

         A  registration  statement on Form S-8,  together with all  amendments,
exhibits and  documents  incorporated  therein by reference  (the  "Registration
Statement"),  has been filed with the Commission,  Washington,  D.C.,  under the
Securities  Act,  with respect to the Shares  offered by this  Prospectus.  This
Prospectus does not contain all the  information  set forth in the  Registration
Statement,  certain parts of which are omitted in accordance  with the rules and
regulations of the Commission.  Statements in this Prospectus as to the contents
of exhibits are not necessarily complete, and each statement is qualified in all
respects  by  reference  to the copies of  documents  filed or  incorporated  by
reference as exhibits to the Registration  Statement or otherwise filed with the
Commission. See also "Incorporation of Certain Documents by Reference."

                 INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

         The following documents (or parts thereof) filed with the Commission by
the Company are incorporated by reference in this Prospectus:

         (a) The  Company's  Registration  Statement on Form 8-A,  dated June 4,
1996, relating to the Common Stock.

         (b) The  Company's  Annual  Report  on Form  10-K,  for the year  ended
December 31, 1997.

         All documents filed by the Company  pursuant to Sections 13(a),  13(c),
or 15(d) of the Exchange Act after the date of this  Prospectus and prior to the
filing of a post-effective  amendment  indicating that all of the Shares offered
hereby have been sold, or  deregistering  all of the Shares that, at the time of
such post-effective amendment, remain unsold, shall be deemed to be incorporated
by reference in this  Prospectus and to be a part hereof from the date of filing
of  such  documents.   Any  statement   contained  herein  or  in  any  document
incorporated  by reference  herein which is deemed to be modified or superseded,
shall not be deemed,  except as so modified or superseded,  to constitute a part
of this Prospectus.

         The Company shall furnish without charge to each person,  including any
beneficial  owner,  to whom a copy of this  Prospectus  is  delivered,  upon the
written or oral  request of such person,  copies of any or all of the  documents
which  are  incorporated  by  reference  herein  (other  than  exhibits  to such
documents,  unless such exhibits are specifically incorporated by reference into
such  documents).  Written or telephone  requests for such  documents  should be
directed  to Ting  Chang,  Vice  President,  Investor  Relations  and  Corporate
Planning, SIS Bancorp, Inc., 1441 Main Street, Springfield, Massachusetts 01102,
telephone (413)748- 8000.

                                        3
<PAGE>
                                   THE COMPANY

General

         The Company is a Massachusetts corporation formed in 1996 and serves as
the bank holding  company for  Springfield  Institution for Savings ("SIS Bank")
and  Glastonbury  Bank & Trust Company  ("GBT").  The Company was formed for the
purpose  of  reorganizing  SIS  Bank  into  a  holding  company  structure  (the
"Reorganization"). Upon the effectiveness of the Reorganization, SIS Bank became
the wholly owned  subsidiary of the Company and SIS Bank's  former  stockholders
became  stockholders  of the Company.  The Company  acquired GBT on December 17,
1997. The only office of the Company,  and its principal  place of business,  is
located  at the  main  office  of SIS  Bank at 1441  Main  Street,  Springfield,
Massachusetts 01102 and its telephone number is (413) 748-8000.

         Established in 1827, SIS Bank is a Massachusetts chartered savings bank
headquartered in Springfield,  Massachusetts. GBT, with its headquarters located
in Glastonbury,  Connecticut, is a Connecticut chartered commercial bank founded
in 1919. Substantially all of the Company's operations are conducted through its
subsidiary banks.

         The Company provides a wide variety of financial  services through both
SIS  Bank  and GBT (the  "Banks"),  including  retail  and  commercial  banking,
residential mortgage origination and servicing, commercial and consumer lending,
merchant  processing  and  insurance  sales.  The Banks serve the  consumers and
businesses located in western  Massachusetts and central  Connecticut  through a
network of 34 full service branches.

         The Company's  revenues are derived  principally from dividend payments
received from the Banks,  which in turn derive their revenues  principally  from
interest  payments  on their  loan  portfolios  and  mortgage-backed  and  other
investment  securities.  The  Banks'  primary  sources  of funds  are  deposits,
borrowings  and  principal  and interest  payments on loans and mortgage  backed
securities.

Property

         The  Company  neither  owns nor  leases any real or  personal  property
directly.  Of the 33 full service branch offices  operated by the Banks,  14 are
owned and 19 are leased.

Competition

         Vigorous competition exists in all areas in which the Company,  through
the  operations  of the Banks,  engages in business.  The Company  faces intense
competition  in its market areas from major banking and financial  institutions,
including many which have  substantially  greater  resources or market  presence
than the Company.  Competitors of the Company include commercial banks,  savings
banks, mutual funds, insurance companies,  finance companies,  credit unions and
mortgage companies.

Employees

         At the present time, the Company does not employ any persons other than
through the Banks.  As of December  31,  1997,  the Banks  employed  622 persons
(full-time equivalent).

                              SELLING SHAREHOLDERS

         The  following  table  sets  forth:   (i)  the  name  of  each  Selling
Shareholder, (ii) his or her position(s) with the Company and its predecessor or
affiliates,  over the last  three  years,  (iii) the  number of shares of Common
Stock owned (or subject to option) by each Selling Shareholder as of the date of
this Prospectus, (iv) the number of shares of Common Stock which, as of the date
of this Prospectus,  may be offered for the account of each Selling  Shareholder
by this  Prospectus  and (v) the amount of the class to be owned by each Selling
Shareholder if such Selling Shareholder were to sell all of the shares of Common
Stock  covered by this  Prospectus.  There can be no  assurance  that any of the
Selling  Shareholders  will  offer  for  sale or sell  any or all of the  Shares
offered by them pursuant to this Prospectus.

                                        4
<PAGE>
<TABLE>
<CAPTION>
                                                                                                       Number       Shares Owned
                                                                                      Shares Owned     of Shares       Following
                                                                                      Prior to This     to be       Completion of
Name                               Position with Company                                 Offering*      Offered       Offering *
-----------------------------      ----------------------------------------------    --------------- -----------  -----------------
<S>                               <C>                                                 <C>              <C>        <C>

Frank W. Barrett                   Executive Vice President, Credit and Commercial      98,600(1.42%)   71,500       27,100**
                                   Lending Group, of the Company and SIS Bank

Ronald E. Bourbeau                 Director of the Company since 1997; Chairman        139,069(2.00%)    6,000      133,069 (1.91%)
                                   of the Board of Directors of GBT

Sister Mary Caritas (Geary) S.P.   Director of the Company and SIS Bank                 11,675**         7,600        4,075**

Ting Chang                         Vice President, Investor Relations and               33,813**        27,000        6,813**
                                   Corporate Planning, of the Company and SIS Bank

Gilbert F. Ehmke                   Senior Vice President and Chief Investment           45,416**        38,100        7,316**
                                   Officer of the Company and SIS Bank

William B. Hart, Jr.               Director of the Company and SIS Bank                 12,400**         7,600        4,800**

Patricia Train Jatkevicius         Vice President, Marketing, or the Company and         8,683**         8,000          683**   
                                   SIS Bank

Charles L. Johnson                 Director of the Company and SIS Bank                 14,800**         7,600        7,200**

Laura Sotir Katz                   Vice President and Controller of the Company         16,728**        12,500        4,228**
                                   and SIS Bank

F. William Marshall, Jr.           President, Chief Executive Officer and Director     195,359(2.81%)  146,300       49,059**
                                   of the Company and SIS Bank

Henry J. McWhinnie                 Senior Vice President, Human Resources Group,        50,377**        35,400       14,977**
                                   of the Company and SIS Bank

John M. Naughton                   Director of the Company and SIS Bank                 29,000**        12,000       17,000**

Thomas O'Brien                     Director of the Company and SIS Bank                 14,413**         7,600        6,813**

Jeanne Rinaldo                     Senior Vice President, Residential Mortgage          47,189**        36,000       11,189**
                                   Group, of the Company and SIS Bank

Brian Schwartz                     Vice President and Director of Internal              12,640**        11,000        1,640**
                                   Auditing of the Company and SIS Bank

Stephen A. Shatz                   Director of the Company and SIS Bank                 25,750**         7,600       18,150**

Christopher A. Sinton              Senior Vice President, Retail Banking Group,         48,427**        37,500       10,927**
                                   of the Company and SIS Bank

J. Gilbert Soucie                  Vice Chairman of the Company since 1997;             77,189(1.11%)   31,000       46,189**
                                   President and Chief Executive Officer of GBT

John F. Treanor                    Executive Vice President, Treasurer and Chief        95,151(1.37%)   73,500       21,651**
                                   Financial Officer of the Company and SIS Bank 
                                   and, since 1998, Chief Operating Officer of 
                                   the Company and SIS Bank

Michael E. Tucker                  Senior Vice President, Clerk and General             44,429**        34,800        9,629**
                                   Counsel of the Company and SIS Bank
---------
<FN>

*  = For purposes of this table, the number of shares owned prior to this  registration  includes all shares,  rounded down to the
     nearest whole share, which are allocated to the shareholder under the Company's Employee Stock Ownership Plan, and those which
     would be owned if all options granted under the Option Plan were exercised.
** = Less than one percent.

</FN>
</TABLE>

                                        5
<PAGE>
                              PLAN OF DISTRIBUTION

         The sales of the Shares by the Selling  Shareholders  may be  effected,
from time to time,  on the NMS or on any stock  exchange on which the Shares may
be  listed  at the  time of sale,  in  negotiated  transactions,  or  through  a
combination  of such methods of sale,  at fixed prices which may be changed,  at
market  prices  prevailing  at the  time of  sale,  at  prices  related  to such
prevailing market prices, or at negotiated prices. The Selling  Shareholders may
effect such  transactions  by selling Shares to or through  broker-dealers,  and
such  broker-dealers  may  receive   compensation  in  the  form  of  discounts,
concessions,  or commissions from the Selling Shareholders and/or the purchasers
of Shares for whom such  broker-dealers may act as agent or to whom they sell as
principal, or both (which compensation as to a particular broker-dealer might be
in excess of customary commissions).

         The Selling  Shareholders and any broker-dealers that act in connection
with the sale of the  Shares  hereunder  might be  deemed  to be  "Underwriters"
within the  meaning of Section  2(11) of the  Securities  Act;  any  commissions
received by them and any profit  realized on the resale of Shares as  principals
might be deemed to be underwriting compensation under the Securities Act.

         Any broker-dealer  acquiring Shares from a Selling Shareholder may sell
the Shares either directly, in its normal market-making  activities,  through or
to other brokers on a principal or agency basis,  or to its customers.  Any such
sales may be at prices then  prevailing  on the NMS,  at prices  related to such
prevailing  market prices,  at negotiated  prices,  or at prices  reflecting the
application of a combination of such methods.

         The Company has advised the Selling Shareholders that anti-manipulative
Rules  10b-5,  10b-6 and 10b-7  promulgated  under the Exchange Act may apply to
their sales in the market.  The Company has furnished  the Selling  Shareholders
with copies of these rules,  and has informed  the Selling  Shareholders  of the
possible need for them to deliver copies of this  Prospectus in connection  with
their resales of the Shares. The Selling  Shareholders may indemnify any broker-
dealer that  participates in  transactions  involving sale of the Shares against
certain liabilities, including liabilities arising under the Securities Act. Any
commissions  paid or any  discounts or  concessions  allowed to any such broker-
dealers,  and, if any such  broker-dealer  purchases shares as a principal,  any
profits  received on the resale of such Shares may be deemed to be  underwriting
discounts and commissions under the Securities Act.

         Upon the Company's being notified by any Selling  Shareholders that any
material  arrangement has been entered into with a broker-dealer for the sale of
Shares through a cross or block trade, a supplemental  prospectus  will be filed
under  Rule  424(c)  under the  Securities  Act,  setting  forth the name of the
participating  broker-dealer(s),  the  number of shares  involved,  the price at
which such Shares were sold by the Selling Shareholder,  the commissions paid or
discounts  or   concessions   allowed  by  the  Selling   Shareholder   to  such
broker-dealer(s),  and where  applicable,  that such  broker-dealer(s),  did not
conduct any investigation to verify the information set out in this Prospectus.

         Any Shares which  qualify for resale  pursuant to Rule 144  promulgated
under the Securities Act may be sold under the Rule rather than pursuant to this
Prospectus.

         There can be no assurance that the Selling  Shareholders  will sell all
or even any of the Shares which may be offered by them or any of them hereunder.

                                 INDEMNIFICATION

         The By-laws of the  Company  provide  for the  indemnification  of each
director,  officer,  employee and agent  against all  expenses  and  liabilities
reasonably  incurred by or imposed on him in connection  with any  proceeding or
threatened  proceeding in which he may become involved by reason of his being or
having been a director or  officer,  so long as such person  acted in good faith
and in a manner  he  reasonably  believed  to be in or not  opposed  to the best
interests of the Company. The By-laws of the Company further provide that (a) if
the Company is merged into or  consolidated  with  another  corporation  and the
Company is not the surviving corporation, the surviving corporation shall assume
the indemnification obligations of the Company under the By-laws with respect to
any action, suit,  proceeding or investigation arising out of or relating to any
actions,  transactions or facts occurring at or prior to the date of such merger
or consolidation;  (b) if the By-laws are invalidated on any ground by any court
of competent jurisdiction,  the Company shall nevertheless indemnify and advance
expenses to each indemnitee as to any expenses (including  reasonable attorneys'
fees), judgments, fines, liabilities,  losses, and amounts paid in settlement in
connection with any action,  suit,  proceeding or investigation,  whether civil,

                                        6
<PAGE>
criminal  or  administrative,  including  an  action  by or in the  right of the
Company,  to the  fullest  extent  permitted  by any  applicable  portion of the
By-laws that have not been  invalidated  and to the fullest extent  permitted by
applicable  law; and (c) if the  Massachusetts  General  Laws are amended  after
adoption  of the  Company's  By-  laws to  expand  further  the  indemnification
permitted to an indemnitee,  the Company shall indemnify all such persons to the
fullest extent permitted by the Massachusetts General Laws, as so amended.

         Insofar as indemnification for liabilities arising under the Securities
Act may be permitted to Directors,  officers, or persons controlling the Company
pursuant to the foregoing provisions,  the Company has been informed that in the
opinion  of the SEC  such  indemnification,  in the  event  of any  such  actual
liability under the Securities Act, is against public policy as expressed in the
Securities Act and is therefore unenforceable.

         The  Articles of the Company  provide that its  directors  shall not be
personally  liable to the Company or its  stockholders  for monetary damages for
breach of fiduciary duty as a director,  except for liability (i) for any breach
of the director's duty of loyalty to the Company or its  stockholders,  (ii) for
acts or omissions not in good faith or which involve intentional misconduct or a
knowing  violation of law, (iii) for any unlawful  distributions to stockholders
or loans to officers or directors,  or (iv) for any  transaction  from which the
director derived an improper personal benefit.

                                     EXPERTS

         The consolidated  balance sheets of the Company as of December 31, 1997
and 1996 and the  related  consolidated  statements  of  operations,  changes in
stockholders'  equity  and cash  flows for each of the  years in the  three-year
period ended  December 31, 1997 included in the Company's  Annual Report on Form
10-K for the year ended December 31, 1997 have been audited by Price  Waterhouse
LLP,  independent  accountants,  as set forth in their report contained therein.
Such financial  statements are incorporated by reference in this Prospectus upon
the authority of such firm as experts in accounting and auditing.

                                  LEGAL MATTERS

         The validity of the Common Stock offered hereby will be passed upon for
the Company by Sullivan & Worcester LLP, Boston, Massachusetts.



                                        7

<PAGE>



                                    EXHIBITS

         The  following   exhibits  are   furnished  in  connection   with  this
Registration Statement:

5        Opinion of Sullivan & Worcester LLP

23.1     Consent of Price Waterhouse LLP

23.3     Consent of Sullivan & Worcester LLP (contained in Exhibit 5)

24       Power of Attorney (included on signature pages)



                                      II-1

<PAGE>

                                   SIGNATURES

         Pursuant  to the  requirements  of the  Securities  Act  of  1933,  the
registrant certifies that it has reasonable grounds to believe that it meets all
of the requirements for filing on Form S-8 and has duly caused this registration
statement  to be  signed  on its  behalf  by  the  undersigned,  thereunto  duly
authorized,  in the City of Springfield,  Commonwealth of Massachusetts,  on the
7th day of May, 1998.

                                     SIS BANCORP, INC.


                                      By:/s/ F. William Marshall, Jr.,
                                           F. William Marshall, Jr.,
                                           President and Chief Executive Officer

         The  undersigned  Officers and  Directors of SIS Bancorp,  Inc.  hereby
severally  constitute F. William  Marshall,  Jr., John F. Treanor and Michael E.
Tucker,  and each of them, acting singly,  our true and lawful attorneys to sign
for us and  in  our  names  in the  capacities  indicated  below  the  Company's
Registration  Statement on Form S-8 and any and all amendments  and  supplements
thereto,  filed with the Securities and Exchange Commission,  granting unto each
of said  attorneys,  acting  singly,  full power and authority to do and perform
each and every act and thing  requisite or necessary to be done in and about the
premises,  as  fully  to all  intents  and  purposes  as he might or could do in
person,  hereby  ratifying and confirming  our  signatures to said  registration
statement  signed by our said  attorneys  and all else that said  attorneys  may
lawfully do and cause to be done by virtue hereof.

         Pursuant  to the  requirements  of the  Securities  Act of  1933,  this
Registration  Statement has been signed below by the following persons on behalf
of the Company and in the capacities and on the dates indicated.
<TABLE>
<CAPTION>
     Signatures                                   Capacity                    Date
     ----------                                   --------                    ----

<S>                                         <C>                             <C>
/s/ F. William Marshall, Jr.                 President, Chief Executive      May 7, 1998
F. William Marshall, Jr.                     Officer and Director


/s/ John F. Treanor                          Treasurer, Chief Financial      May 7, 1998
John F. Treanor                              Officer and Chief Operating
                                             Officer (principal accounting
                                             officer)

/s/ Ronald E. Bourbeau                       Director                        May 7, 1998
Ronald E. Bourbeau


/s/ Sister Mary Caritas (Geary) S.P.         Director                        May 7, 1998
Sister Mary Caritas (Geary) S.P.


/s/ William B. Hart, Jr.                     Director                        May 7, 1998
William B. Hart, Jr.

                                      II-2
<PAGE>


/s/ Charles L. Johnson                       Director                        May 7, 1998
Charles L. Johnson


/s/ John M. Naughton                         Director                        May 7, 1998
John M. Naughton


/s/ Thomas O'Brien                           Director                        May 7, 1998
Thomas O'Brien


/s/ Stephen A. Shatz                         Director                        May 7, 1998
Stephen A. Shatz
</TABLE>

                                      II-3
[{"type": "S-8", "sequence": "1", "secsgml_size_bytes": 35566}]
{"company-data": {"conformed-name": "SIS BANCORP INC", "cik": "0001013049", "assigned-sic": "6036", "irs-number": "043303264", "state-of-incorporation": "MA", "fiscal-year-end": "1231"}, "filing-values": {"form-type": "S-8", "act": "33", "file-number": "333-52133", "film-number": "98613390"}, "business-address": {"street1": "P O BOX 3034", "street2": "1441 MAIN STREET", "city": "SPRINGFIELD", "state": "MA", "zip": "01102-3034", "phone": "4137488000"}, "mail-address": {"street1": "1441 MAIN STREET", "city": "SPRINGFIELD", "state": "MA", "zip": "01102"}}
As filed with the Securities and Exchange Commission on May 8, 1998
                                             Registration No. 333-

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                         -------------------------------

                                    FORM S-8
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933

                                SIS BANCORP, INC.
             (Exact name of Registrant as Specified in Its Charter)

          Massachusetts                          04-3303264
  (State or other jurisdiction of        (I.R.S. Employer  Identification No.)
  incorporation or organization)

                                1441 Main Street
                        Springfield, Massachusetts 01102
                    (Address of Principal Executive Offices)

                       SIS Bancorp, Inc. Stock Option Plan
                  (as amended and restated as of March 1, 1998)
                            (Full Title of the Plan)

                             MICHAEL E. TUCKER, ESQ.
                    Senior Vice President and General Counsel
                                SIS Bancorp, Inc.
                                1441 Main Street
                        Springfield, Massachusetts 01102
                     (Name and Address of Agent For Service)

                                  (413)748-8000
          (Telephone number, including area code, of agent for service)

                                    Copy to:
                             STEPHEN J. COUKOS, ESQ.
                            Sullivan & Worcester LLP
                             One Post Office Square
                           Boston, Massachusetts 02109
CALCULATION OF REGISTRATION FEE

                                                                  Proposed Maximum          Proposed Maximum
                                            Amount to be         Offering Price Per        Aggregate Offering          Amount of
  Title of Securities to be Registered       Registered                Share                     Price             Registration Fee
Common Stock, $.01 par value                340,000 (1)               $42.50 (2)           $14,450,000.00 (2)         $4,262.75
(1) Represents the additional  number of shares of Common Stock authorized  under the Stock Option Plan, as amended and restated.  A
total number of 806,250  additional  shares authorized under the Stock Option Plan were previously  registered  pursuant to Form S-8
Registration  Statement No. 333-11443.  See also "Explanatory Note" below. Also includes an indeterminate number of securities which
may be issuable by reason of a reorganization,  recapitalization, exchange of shares, stock split, combination of shares or dividend
payable in shares of Common Stock or other securities, as provided under the plans.

(2) Pursuant to Rule 457(h) the offering price is calculated based upon the average of the bid and asked prices of the Common Stock
as reported on the National Association of Securities Dealers Automated Quotation, National Market System on May 5, 1998.
EXPLANATORY NOTE

         This Registration  Statement is filed pursuant to General Instruction E
of Form S-8. A Form S-8 Registration  Statement,  No. 333-11443,  was previously
filed on September  5, 1996 to register a total of 868,650  shares of the common
stock, par value $0.01 per share (the "Common Stock"), of SIS Bancorp, Inc. (the
"Company"),  of which 806,250 shares were  authorized  for issuance  pursuant to
options  granted or to be granted  under the Company's  Director and  Management
Stock Option Plans (the "Prior  Plans").  On February  18, 1998,  the  Company's
Board of Directors  approved  the  Company's  Stock Option Plan,  as amended and
restated (the "Current  Plan"),  which,  among other changes to the Prior Plans,
consolidated  the Prior  Plans into the  Current  Plan and  increased  the total
number of shares of Common Stock previously  authorized under the Prior Plans by
340,000 shares.  The Current Plan was approved by the Company's  stockholders on
May 7, 1998. A total of  1,146,250  shares of Common  Stock are  authorized  for
issuance  pursuant to options that may be granted under the Current Plan,  which
includes all options previously granted under the Prior Plans.

         This Registration  Statement,  in accordance with General Instruction E
of Form S-8,  incorporates  by  reference  the  contents  of the prior  Form S-8
Registration  Statement,  No.  333-11443,  referenced  above.  This Registration
Statement  also  contains  a  Prospectus,   prepared  in  accordance   with  the
requirements  of Part I of Form S-3 (in accordance with Section C of the General
Instructions  to Form S-8),  which covers  re-offers and re-sales by the Selling
Shareholders  listed in the Prospectus of shares of the Common Stock that may be
either issued directly to certain directors and/or executive  officers under the
Company's  Director and Management  Restricted  Stock Plans or issued to certain
directors  and/or  executive  officers  pursuant  to their  exercise  of options
granted under the Current Plan, including options granted under the Prior Plans.
Prospectus       
                                 618,600 Shares

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

                                SIS BANCORP, INC.

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

                                  COMMON STOCK
                           (Par Value $.01 Per Share)
                            -------------------------

         This  Prospectus  is being used in connection  with the offering,  from
time to time,  by  certain  shareholders  (the  "Selling  Shareholders")  of SIS
Bancorp, Inc. (the "Company"),  of up to 618,600 shares (the "Shares") of common
stock,  par value $.01 per share (the "Common  Stock"),  of the  Company,  which
either have been  acquired by certain  directors  and  executives of the Company
under the SIS Bancorp,  Inc.  Director and Management  Restricted Stock Plans or
may be acquired  pursuant to the exercise of options (the "Options")  granted to
certain  directors and  executives  of the Company  under the SIS Bancorp,  Inc.
Stock  Option  Plan,  as amended and  restated as of March 1, 1998 (the  "Option
Plan"),  which includes  Options  granted under the Company's prior Director and
Management  Stock Option Plans. The Company will not receive any of the proceeds
from the sale of the Shares by the Selling Shareholders.

         The Shares may be sold from time to time by the Selling Shareholders or
by pledgees, donees, transferees or other successors in interest. Such sales may
be made on the National  Association of Securities Dealers Automated  Quotation,
National  Market  System  ("NMS") at prices and at terms then  prevailing  or at
prices related to the then current market price, or in negotiated  transactions.
All discounts,  commissions or fees incurred in connection  with the sale of the
Shares  offered  hereby  will  be  paid by the  Selling  Shareholders  or by the
purchasers of the Shares,  except that the expenses of preparing and filing this
Prospectus  and the  related  Registration  Statement  with the  Securities  and
Exchange  Commission  (the  "Commission"),  and of registering or qualifying the
Shares will be paid by the Company.

         The Selling  Shareholders  and any broker  executing  selling orders on
behalf of the Selling  Shareholders may be deemed to be an "underwriter"  within
the meaning of the Securities Act of 1933, as amended (the "Securities Act"), in
which event any discounts,  concessions,  or commissions received by such broker
may be deemed to be underwriting commissions under the Securities Act.

         The  Common  Stock is listed on the NMS.  On May 5, 1998,  the  closing
price of the Common Stock on the NMS was $42.625 per share.

  THESE SECURITIES HAVE NOT BEEN APPROVED OR DISAPPROVED BY THE SECURITIES AND
   EXCHANGE COMMISSION, THE FEDERAL DEPOSIT INSURANCE CORPORATION OR ANY STATE
    SECURITIES COMMISSION, NOR HAS THE COMMISSION, CORPORATION, OR ANY STATE
 SECURITIES COMMISSION PASSED UPON THE ACCURACY OR ADEQUACY OF THIS PROSPECTUS.
            ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

 THE SHARES OF COMMON STOCK OFFERED BY THIS PROSPECTUS ARE NOT SAVINGS ACCOUNTS
  OR DEPOSITS AND ARE NOT INSURED BY THE FEDERAL DEPOSIT INSURANCE CORPORATION,
  THE BANK INSURANCE FUND, THE SAVINGS ASSOCIATION INSURANCE FUND OR ANY OTHER
    GOVERNMENTAL AGENCY, AND INVOLVE INVESTMENT RISK, INCLUDING THE POSSIBLE
                               LOSS OF PRINCIPAL.

                  The date of this Prospectus is May 8, 1998.
No person has been  authorized to give any  information  or to make any
representation  not contained in this  Prospectus,  and, if given or made,  such
information or representation  must not be relied upon as having been authorized
by the  Company.  This  Prospectus  does  not  constitute  an offer to sell or a
solicitation  of an offer to buy any  securities  other  than the  Common  Stock
offered by this  Prospectus or an offer to sell or a solicitation of an offer to
buy such Common Stock in any  jurisdiction  to any person to whom it is unlawful
to make such offer or solicitation in such jurisdiction. Neither the delivery of
this  Prospectus nor any sale made  hereunder  shall,  under any  circumstances,
create  any  implication  that  there has been no change in the  affairs  of the
Company or that the  information  herein is correct as of any time subsequent to
the date hereof.

                                TABLE OF CONTENTS

Section                                                                    Page

Available Information ..................................................     3

Incorporation of Certain Documents by Reference ........................     3

The Company ............................................................     4

Selling Shareholders ...................................................     4

Plan of Distribution ...................................................     6

Indemnification ........................................................     6

Experts ................................................................     7

Legal Matters ..........................................................     7

                                        2
AVAILABLE INFORMATION

         The  Company  is  subject  to  the  informational  requirements  of the
Securities  Exchange  Act of 1934,  as amended  (the  "Exchange  Act"),  and, in
accordance  therewith,  files reports,  proxy statements,  and other information
with the Commission.  Such reports, proxy statements,  and other information can
be inspected  and copied at the public  reference  facilities  maintained by the
Commission  at 450  Fifth  Street,  N.W.,  Washington,  D.C.  20549,  and at the
following  Regional Offices:  the Northeast  Regional Office,  Seven World Trade
Center,  Suite 1300, New York, New York 10048,  and the Midwest Regional Office,
Citicorp  Center,  500  West  Madison  Street,  Suite  1400,  Chicago,  Illinois
60661-2511.  Copies of such material can be obtained by written request from the
Public  Reference  Section  of  the  Commission  at  450  Fifth  Street,   N.W.,
Washington,  D.C. 20549. The Company files  electronically  with the Commission.
The Commisssion maintains a World Wide Web site (located at  http://www.sec.gov)
that contains  reports,  proxy and information  statements and other information
regarding registrants that file electronically with the Commission.

         A  registration  statement on Form S-8,  together with all  amendments,
exhibits and  documents  incorporated  therein by reference  (the  "Registration
Statement"),  has been filed with the Commission,  Washington,  D.C.,  under the
Securities  Act,  with respect to the Shares  offered by this  Prospectus.  This
Prospectus does not contain all the  information  set forth in the  Registration
Statement,  certain parts of which are omitted in accordance  with the rules and
regulations of the Commission.  Statements in this Prospectus as to the contents
of exhibits are not necessarily complete, and each statement is qualified in all
respects  by  reference  to the copies of  documents  filed or  incorporated  by
reference as exhibits to the Registration  Statement or otherwise filed with the
Commission. See also "Incorporation of Certain Documents by Reference."

                 INCORPORATION OF CERTAIN DOCUMENTS BY REFERENCE

         The following documents (or parts thereof) filed with the Commission by
the Company are incorporated by reference in this Prospectus:

         (a) The  Company's  Registration  Statement on Form 8-A,  dated June 4,
1996, relating to the Common Stock.

         (b) The  Company's  Annual  Report  on Form  10-K,  for the year  ended
December 31, 1997.

         All documents filed by the Company  pursuant to Sections 13(a),  13(c),
or 15(d) of the Exchange Act after the date of this  Prospectus and prior to the
filing of a post-effective  amendment  indicating that all of the Shares offered
hereby have been sold, or  deregistering  all of the Shares that, at the time of
such post-effective amendment, remain unsold, shall be deemed to be incorporated
by reference in this  Prospectus and to be a part hereof from the date of filing
of  such  documents.   Any  statement   contained  herein  or  in  any  document
incorporated  by reference  herein which is deemed to be modified or superseded,
shall not be deemed,  except as so modified or superseded,  to constitute a part
of this Prospectus.

         The Company shall furnish without charge to each person,  including any
beneficial  owner,  to whom a copy of this  Prospectus  is  delivered,  upon the
written or oral  request of such person,  copies of any or all of the  documents
which  are  incorporated  by  reference  herein  (other  than  exhibits  to such
documents,  unless such exhibits are specifically incorporated by reference into
such  documents).  Written or telephone  requests for such  documents  should be
directed  to Ting  Chang,  Vice  President,  Investor  Relations  and  Corporate
Planning, SIS Bancorp, Inc., 1441 Main Street, Springfield, Massachusetts 01102,
telephone (413)748- 8000.

                                        3
THE COMPANY

General

         The Company is a Massachusetts corporation formed in 1996 and serves as
the bank holding  company for  Springfield  Institution for Savings ("SIS Bank")
and  Glastonbury  Bank & Trust Company  ("GBT").  The Company was formed for the
purpose  of  reorganizing  SIS  Bank  into  a  holding  company  structure  (the
"Reorganization"). Upon the effectiveness of the Reorganization, SIS Bank became
the wholly owned  subsidiary of the Company and SIS Bank's  former  stockholders
became  stockholders  of the Company.  The Company  acquired GBT on December 17,
1997. The only office of the Company,  and its principal  place of business,  is
located  at the  main  office  of SIS  Bank at 1441  Main  Street,  Springfield,
Massachusetts 01102 and its telephone number is (413) 748-8000.

         Established in 1827, SIS Bank is a Massachusetts chartered savings bank
headquartered in Springfield,  Massachusetts. GBT, with its headquarters located
in Glastonbury,  Connecticut, is a Connecticut chartered commercial bank founded
in 1919. Substantially all of the Company's operations are conducted through its
subsidiary banks.

         The Company provides a wide variety of financial  services through both
SIS  Bank  and GBT (the  "Banks"),  including  retail  and  commercial  banking,
residential mortgage origination and servicing, commercial and consumer lending,
merchant  processing  and  insurance  sales.  The Banks serve the  consumers and
businesses located in western  Massachusetts and central  Connecticut  through a
network of 34 full service branches.

         The Company's  revenues are derived  principally from dividend payments
received from the Banks,  which in turn derive their revenues  principally  from
interest  payments  on their  loan  portfolios  and  mortgage-backed  and  other
investment  securities.  The  Banks'  primary  sources  of funds  are  deposits,
borrowings  and  principal  and interest  payments on loans and mortgage  backed
securities.

Property

         The  Company  neither  owns nor  leases any real or  personal  property
directly.  Of the 33 full service branch offices  operated by the Banks,  14 are
owned and 19 are leased.

Competition

         Vigorous competition exists in all areas in which the Company,  through
the  operations  of the Banks,  engages in business.  The Company  faces intense
competition  in its market areas from major banking and financial  institutions,
including many which have  substantially  greater  resources or market  presence
than the Company.  Competitors of the Company include commercial banks,  savings
banks, mutual funds, insurance companies,  finance companies,  credit unions and
mortgage companies.

Employees

         At the present time, the Company does not employ any persons other than
through the Banks.  As of December  31,  1997,  the Banks  employed  622 persons
(full-time equivalent).

                              SELLING SHAREHOLDERS

         The  following  table  sets  forth:   (i)  the  name  of  each  Selling
Shareholder, (ii) his or her position(s) with the Company and its predecessor or
affiliates,  over the last  three  years,  (iii) the  number of shares of Common
Stock owned (or subject to option) by each Selling Shareholder as of the date of
this Prospectus, (iv) the number of shares of Common Stock which, as of the date
of this Prospectus,  may be offered for the account of each Selling  Shareholder
by this  Prospectus  and (v) the amount of the class to be owned by each Selling
Shareholder if such Selling Shareholder were to sell all of the shares of Common
Stock  covered by this  Prospectus.  There can be no  assurance  that any of the
Selling  Shareholders  will  offer  for  sale or sell  any or all of the  Shares
offered by them pursuant to this Prospectus.

                                        4
Number       Shares Owned
                                                                                      Shares Owned     of Shares       Following
                                                                                      Prior to This     to be       Completion of
Name                               Position with Company                                 Offering*      Offered       Offering *
-----------------------------      ----------------------------------------------    --------------- -----------  -----------------
Frank W. Barrett                   Executive Vice President, Credit and Commercial      98,600(1.42%)   71,500       27,100**
                                   Lending Group, of the Company and SIS Bank

Ronald E. Bourbeau                 Director of the Company since 1997; Chairman        139,069(2.00%)    6,000      133,069 (1.91%)
                                   of the Board of Directors of GBT

Sister Mary Caritas (Geary) S.P.   Director of the Company and SIS Bank                 11,675**         7,600        4,075**

Ting Chang                         Vice President, Investor Relations and               33,813**        27,000        6,813**
                                   Corporate Planning, of the Company and SIS Bank

Gilbert F. Ehmke                   Senior Vice President and Chief Investment           45,416**        38,100        7,316**
                                   Officer of the Company and SIS Bank

William B. Hart, Jr.               Director of the Company and SIS Bank                 12,400**         7,600        4,800**

Patricia Train Jatkevicius         Vice President, Marketing, or the Company and         8,683**         8,000          683**   
                                   SIS Bank

Charles L. Johnson                 Director of the Company and SIS Bank                 14,800**         7,600        7,200**

Laura Sotir Katz                   Vice President and Controller of the Company         16,728**        12,500        4,228**
                                   and SIS Bank

F. William Marshall, Jr.           President, Chief Executive Officer and Director     195,359(2.81%)  146,300       49,059**
                                   of the Company and SIS Bank

Henry J. McWhinnie                 Senior Vice President, Human Resources Group,        50,377**        35,400       14,977**
                                   of the Company and SIS Bank

John M. Naughton                   Director of the Company and SIS Bank                 29,000**        12,000       17,000**

Thomas O'Brien                     Director of the Company and SIS Bank                 14,413**         7,600        6,813**

Jeanne Rinaldo                     Senior Vice President, Residential Mortgage          47,189**        36,000       11,189**
                                   Group, of the Company and SIS Bank

Brian Schwartz                     Vice President and Director of Internal              12,640**        11,000        1,640**
                                   Auditing of the Company and SIS Bank

Stephen A. Shatz                   Director of the Company and SIS Bank                 25,750**         7,600       18,150**

Christopher A. Sinton              Senior Vice President, Retail Banking Group,         48,427**        37,500       10,927**
                                   of the Company and SIS Bank

J. Gilbert Soucie                  Vice Chairman of the Company since 1997;             77,189(1.11%)   31,000       46,189**
                                   President and Chief Executive Officer of GBT

John F. Treanor                    Executive Vice President, Treasurer and Chief        95,151(1.37%)   73,500       21,651**
                                   Financial Officer of the Company and SIS Bank 
                                   and, since 1998, Chief Operating Officer of 
                                   the Company and SIS Bank

Michael E. Tucker                  Senior Vice President, Clerk and General             44,429**        34,800        9,629**
                                   Counsel of the Company and SIS Bank
---------
*  = For purposes of this table, the number of shares owned prior to this  registration  includes all shares,  rounded down to the
     nearest whole share, which are allocated to the shareholder under the Company's Employee Stock Ownership Plan, and those which
     would be owned if all options granted under the Option Plan were exercised.
** = Less than one percent.
5
PLAN OF DISTRIBUTION

         The sales of the Shares by the Selling  Shareholders  may be  effected,
from time to time,  on the NMS or on any stock  exchange on which the Shares may
be  listed  at the  time of sale,  in  negotiated  transactions,  or  through  a
combination  of such methods of sale,  at fixed prices which may be changed,  at
market  prices  prevailing  at the  time of  sale,  at  prices  related  to such
prevailing market prices, or at negotiated prices. The Selling  Shareholders may
effect such  transactions  by selling Shares to or through  broker-dealers,  and
such  broker-dealers  may  receive   compensation  in  the  form  of  discounts,
concessions,  or commissions from the Selling Shareholders and/or the purchasers
of Shares for whom such  broker-dealers may act as agent or to whom they sell as
principal, or both (which compensation as to a particular broker-dealer might be
in excess of customary commissions).

         The Selling  Shareholders and any broker-dealers that act in connection
with the sale of the  Shares  hereunder  might be  deemed  to be  "Underwriters"
within the  meaning of Section  2(11) of the  Securities  Act;  any  commissions
received by them and any profit  realized on the resale of Shares as  principals
might be deemed to be underwriting compensation under the Securities Act.

         Any broker-dealer  acquiring Shares from a Selling Shareholder may sell
the Shares either directly, in its normal market-making  activities,  through or
to other brokers on a principal or agency basis,  or to its customers.  Any such
sales may be at prices then  prevailing  on the NMS,  at prices  related to such
prevailing  market prices,  at negotiated  prices,  or at prices  reflecting the
application of a combination of such methods.

         The Company has advised the Selling Shareholders that anti-manipulative
Rules  10b-5,  10b-6 and 10b-7  promulgated  under the Exchange Act may apply to
their sales in the market.  The Company has furnished  the Selling  Shareholders
with copies of these rules,  and has informed  the Selling  Shareholders  of the
possible need for them to deliver copies of this  Prospectus in connection  with
their resales of the Shares. The Selling  Shareholders may indemnify any broker-
dealer that  participates in  transactions  involving sale of the Shares against
certain liabilities, including liabilities arising under the Securities Act. Any
commissions  paid or any  discounts or  concessions  allowed to any such broker-
dealers,  and, if any such  broker-dealer  purchases shares as a principal,  any
profits  received on the resale of such Shares may be deemed to be  underwriting
discounts and commissions under the Securities Act.

         Upon the Company's being notified by any Selling  Shareholders that any
material  arrangement has been entered into with a broker-dealer for the sale of
Shares through a cross or block trade, a supplemental  prospectus  will be filed
under  Rule  424(c)  under the  Securities  Act,  setting  forth the name of the
participating  broker-dealer(s),  the  number of shares  involved,  the price at
which such Shares were sold by the Selling Shareholder,  the commissions paid or
discounts  or   concessions   allowed  by  the  Selling   Shareholder   to  such
broker-dealer(s),  and where  applicable,  that such  broker-dealer(s),  did not
conduct any investigation to verify the information set out in this Prospectus.

         Any Shares which  qualify for resale  pursuant to Rule 144  promulgated
under the Securities Act may be sold under the Rule rather than pursuant to this
Prospectus.

         There can be no assurance that the Selling  Shareholders  will sell all
or even any of the Shares which may be offered by them or any of them hereunder.

                                 INDEMNIFICATION

         The By-laws of the  Company  provide  for the  indemnification  of each
director,  officer,  employee and agent  against all  expenses  and  liabilities
reasonably  incurred by or imposed on him in connection  with any  proceeding or
threatened  proceeding in which he may become involved by reason of his being or
having been a director or  officer,  so long as such person  acted in good faith
and in a manner  he  reasonably  believed  to be in or not  opposed  to the best
interests of the Company. The By-laws of the Company further provide that (a) if
the Company is merged into or  consolidated  with  another  corporation  and the
Company is not the surviving corporation, the surviving corporation shall assume
the indemnification obligations of the Company under the By-laws with respect to
any action, suit,  proceeding or investigation arising out of or relating to any
actions,  transactions or facts occurring at or prior to the date of such merger
or consolidation;  (b) if the By-laws are invalidated on any ground by any court
of competent jurisdiction,  the Company shall nevertheless indemnify and advance
expenses to each indemnitee as to any expenses (including  reasonable attorneys'
fees), judgments, fines, liabilities,  losses, and amounts paid in settlement in
connection with any action,  suit,  proceeding or investigation,  whether civil,

                                        6
criminal  or  administrative,  including  an  action  by or in the  right of the
Company,  to the  fullest  extent  permitted  by any  applicable  portion of the
By-laws that have not been  invalidated  and to the fullest extent  permitted by
applicable  law; and (c) if the  Massachusetts  General  Laws are amended  after
adoption  of the  Company's  By-  laws to  expand  further  the  indemnification
permitted to an indemnitee,  the Company shall indemnify all such persons to the
fullest extent permitted by the Massachusetts General Laws, as so amended.

         Insofar as indemnification for liabilities arising under the Securities
Act may be permitted to Directors,  officers, or persons controlling the Company
pursuant to the foregoing provisions,  the Company has been informed that in the
opinion  of the SEC  such  indemnification,  in the  event  of any  such  actual
liability under the Securities Act, is against public policy as expressed in the
Securities Act and is therefore unenforceable.

         The  Articles of the Company  provide that its  directors  shall not be
personally  liable to the Company or its  stockholders  for monetary damages for
breach of fiduciary duty as a director,  except for liability (i) for any breach
of the director's duty of loyalty to the Company or its  stockholders,  (ii) for
acts or omissions not in good faith or which involve intentional misconduct or a
knowing  violation of law, (iii) for any unlawful  distributions to stockholders
or loans to officers or directors,  or (iv) for any  transaction  from which the
director derived an improper personal benefit.

                                     EXPERTS

         The consolidated  balance sheets of the Company as of December 31, 1997
and 1996 and the  related  consolidated  statements  of  operations,  changes in
stockholders'  equity  and cash  flows for each of the  years in the  three-year
period ended  December 31, 1997 included in the Company's  Annual Report on Form
10-K for the year ended December 31, 1997 have been audited by Price  Waterhouse
LLP,  independent  accountants,  as set forth in their report contained therein.
Such financial  statements are incorporated by reference in this Prospectus upon
the authority of such firm as experts in accounting and auditing.

                                  LEGAL MATTERS

         The validity of the Common Stock offered hereby will be passed upon for
the Company by Sullivan & Worcester LLP, Boston, Massachusetts.

                                        7
EXHIBITS

         The  following   exhibits  are   furnished  in  connection   with  this
Registration Statement:

5        Opinion of Sullivan & Worcester LLP

23.1     Consent of Price Waterhouse LLP

23.3     Consent of Sullivan & Worcester LLP (contained in Exhibit 5)

24       Power of Attorney (included on signature pages)

                                      II-1
SIGNATURES

         Pursuant  to the  requirements  of the  Securities  Act  of  1933,  the
registrant certifies that it has reasonable grounds to believe that it meets all
of the requirements for filing on Form S-8 and has duly caused this registration
statement  to be  signed  on its  behalf  by  the  undersigned,  thereunto  duly
authorized,  in the City of Springfield,  Commonwealth of Massachusetts,  on the
7th day of May, 1998.

                                     SIS BANCORP, INC.

                                      By:/s/ F. William Marshall, Jr.,
                                           F. William Marshall, Jr.,
                                           President and Chief Executive Officer

         The  undersigned  Officers and  Directors of SIS Bancorp,  Inc.  hereby
severally  constitute F. William  Marshall,  Jr., John F. Treanor and Michael E.
Tucker,  and each of them, acting singly,  our true and lawful attorneys to sign
for us and  in  our  names  in the  capacities  indicated  below  the  Company's
Registration  Statement on Form S-8 and any and all amendments  and  supplements
thereto,  filed with the Securities and Exchange Commission,  granting unto each
of said  attorneys,  acting  singly,  full power and authority to do and perform
each and every act and thing  requisite or necessary to be done in and about the
premises,  as  fully  to all  intents  and  purposes  as he might or could do in
person,  hereby  ratifying and confirming  our  signatures to said  registration
statement  signed by our said  attorneys  and all else that said  attorneys  may
lawfully do and cause to be done by virtue hereof.

         Pursuant  to the  requirements  of the  Securities  Act of  1933,  this
Registration  Statement has been signed below by the following persons on behalf
of the Company and in the capacities and on the dates indicated.
Signatures                                   Capacity                    Date
     ----------                                   --------                    ----
/s/ F. William Marshall, Jr.                 President, Chief Executive      May 7, 1998
F. William Marshall, Jr.                     Officer and Director

/s/ John F. Treanor                          Treasurer, Chief Financial      May 7, 1998
John F. Treanor                              Officer and Chief Operating
                                             Officer (principal accounting
                                             officer)

/s/ Ronald E. Bourbeau                       Director                        May 7, 1998
Ronald E. Bourbeau

/s/ Sister Mary Caritas (Geary) S.P.         Director                        May 7, 1998
Sister Mary Caritas (Geary) S.P.

/s/ William B. Hart, Jr.                     Director                        May 7, 1998
William B. Hart, Jr.

                                      II-2
/s/ Charles L. Johnson                       Director                        May 7, 1998
Charles L. Johnson

/s/ John M. Naughton                         Director                        May 7, 1998
John M. Naughton

/s/ Thomas O'Brien                           Director                        May 7, 1998
Thomas O'Brien

/s/ Stephen A. Shatz                         Director                        May 7, 1998
Stephen A. Shatz
II-3