<PAGE> 1



                               GUARANTEE AGREEMENT

                              CENTRAL BANCORP, INC.

                         Dated as of September 16, 2004





<PAGE> 2

                                TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                                    PAGE


                                                 ARTICLE I
                                       DEFINITIONS AND INTERPRETATION
<S>               <C>
SECTION 1.1.      Definitions and Interpretation......................................1

                                                 ARTICLE II
                              POWERS, DUTIES AND RIGHTS OF THE GUARANTEE TRUSTEE

SECTION 2.1.      Powers and Duties of the Guarantee Trustee..........................4

SECTION 2.2.      Certain Rights of the Guarantee Trustee.............................5

SECTION 2.3.      Not Responsible for Recitals or Issuance of Guarantee...............7

SECTION 2.4.      Events of Default; Waiver...........................................7

SECTION 2.5.      Events of Default; Notice...........................................8

                                                 ARTICLE III
                                            THE GUARANTEE TRUSTEE

SECTION 3.1.      The Guarantee Trustee; Eligibility..................................8

SECTION 3.2.      Appointment, Removal and Resignation of the Guarantee Trustee.......9

                                                 ARTICLE IV
                                                 GUARANTEE

SECTION 4.1.      Guarantee...........................................................9

SECTION 4.2.      Waiver of Notice and Demand........................................10

SECTION 4.3.      Obligations Not Affected...........................................10

SECTION 4.4.      Rights of Holders..................................................11

SECTION 4.5.      Guarantee of Payment...............................................11

SECTION 4.6.      Subrogation........................................................11

SECTION 4.7.      Independent Obligations............................................12

SECTION 4.8.      Enforcement........................................................12

</TABLE>


                                      -i-

<PAGE> 3

<TABLE>
<CAPTION>
                               TABLE OF CONTENTS
                                  (continued)


                                                 ARTICLE V
                                   LIMITATION OF TRANSACTIONS; SUBORDINATION
<S>               <C>
SECTION 5.1.      Limitation of Transactions.........................................12

SECTION 5.2.      Ranking............................................................13

                                                 ARTICLE VI
                                                TERMINATION

SECTION 6.1.      Termination........................................................13

                                                 ARTICLE VII
                                               INDEMNIFICATION

SECTION 7.1.      Exculpation........................................................14

SECTION 7.2.      Indemnification....................................................14

SECTION 7.3.      Compensation; Reimbursement of Expenses............................15

                                                 ARTICLE VIII
                                                 MISCELLANEOUS

SECTION 8.1.      Successors and Assigns.............................................16

SECTION 8.2.      Amendments.........................................................16

SECTION 8.3.      Notices............................................................16

SECTION 8.4.      Benefit............................................................17

SECTION 8.5.      Governing Law......................................................17

SECTION 8.6.      Counterparts.......................................................17

</TABLE>

                                      -ii-

<PAGE> 4


                               GUARANTEE AGREEMENT
                               -------------------

         This GUARANTEE  AGREEMENT (the "Guarantee"),  dated as of September 16,
2004,  is executed  and  delivered by Central  Bancorp,  Inc.,  incorporated  in
Massachusetts  (the  "Guarantor"),  and  JPMorgan  Chase Bank,  as trustee  (the
"Guarantee  Trustee"),  for the benefit of the Holders (as defined  herein) from
time to time of the Capital  Securities (as defined  herein) of Central  Bancorp
Capital Trust I, a Delaware statutory trust (the "Issuer").

         WHEREAS,  pursuant to an Amended and Restated Declaration of Trust (the
"Declaration"), dated as of September 16, 2004, among the trustees named therein
of the Issuer,  Central Bancorp,  Inc., as sponsor, and the Holders from time to
time of undivided  beneficial  interests in the assets of the Issuer, the Issuer
is issuing on the date hereof securities, having an aggregate liquidation amount
of up to $5,100,000,  designated the TP Securities  (the "Capital  Securities");
and

         WHEREAS,   as  incentive  for  the  Holders  to  purchase  the  Capital
Securities,  the Guarantor desires  irrevocably and unconditionally to agree, to
the  extent  set  forth in this  Guarantee,  to pay to the  Holders  of  Capital
Securities the Guarantee  Payments (as defined herein) and to make certain other
payments on the terms and conditions set forth herein.

         NOW, THEREFORE,  in consideration of the purchase by each Holder of the
Capital Securities, which purchase the Guarantor hereby agrees shall benefit the
Guarantor, the Guarantor executes and delivers this Guarantee for the benefit of
the Holders.

                                    ARTICLE I
                         DEFINITIONS AND INTERPRETATION

SECTION 1.1.    Definitions and Interpretation.
                ------------------------------

         In this Guarantee, unless the context otherwise requires:

         (a)  capitalized  terms used in this  Guarantee  but not defined in the
    preamble above have the respective meanings assigned to them in this Section
    1.1;

         (b)  a term defined  anywhere in this  Guarantee  has the same  meaning
    throughout;

         (c)  all references to "the Guarantee" or "this  Guarantee" are to this
    Guarantee as modified, supplemented or amended from time to time;

         (d)  all references  in this  Guarantee to Articles and Sections are to
    Articles and Sections of this Guarantee, unless otherwise specified;

         (e)  terms defined in the  Declaration  as of the date of  execution of
    this  Guarantee have the same meanings when used in this  Guarantee,  unless
    otherwise  defined  in  this  Guarantee  or  unless  the  context  otherwise
    requires; and

         (f)  a reference to the singular includes the plural and vice versa.

<PAGE> 5

         "Beneficiaries"  means any  Person to whom the  Issuer is or  hereafter
becomes indebted or liable.

         "Corporate  Trust Office" means the office of the Guarantee  Trustee at
which the  corporate  trust  business of the  Guarantee  Trustee  shall,  at any
particular time, be principally administered.

         "Covered Person" means any Holder of Capital Securities.

         "Debentures"  means  the  junior  subordinated  debentures  of  Central
Bancorp, Inc., designated the Junior Subordinated Debt Securities due 2034, held
by the Institutional Trustee (as defined in the Declaration) of the Issuer.

         "Event of Default" has the meaning set forth in Section 2.4.

         "Guarantee  Payments"  means the following  payments or  distributions,
without duplication,  with respect to the Capital Securities,  to the extent not
paid or made by the Issuer: (i) any accrued and unpaid Distributions (as defined
in the Declaration)  which are required to be paid on such Capital Securities to
the extent the Issuer has funds available in the Property Account (as defined in
the Declaration) therefor at such time, (ii) the Redemption Price (as defined in
the  Indenture)  to the extent the Issuer has funds  available  in the  Property
Account therefor at such time, with respect to any Capital Securities called for
redemption by the Issuer,  (iii) the Special Redemption Price (as defined in the
Indenture) to the extent the Issuer has funds available in the Property  Account
therefor at such time, with respect to Capital  Securities called for redemption
upon the occurrence of a Special Event (as defined in the  Indenture),  and (iv)
upon  a  voluntary  or  involuntary  liquidation,   dissolution,  winding-up  or
termination  of the Issuer (other than in connection  with the  distribution  of
Debentures  to the Holders of the  Capital  Securities  in exchange  therefor as
provided in the Declaration), the lesser of (a) the aggregate of the liquidation
amount and all accrued and unpaid Distributions on the Capital Securities to the
date of payment,  to the extent the Issuer has funds  available  in the Property
Account  therefor  at such  time,  and (b) the  amount of  assets of the  Issuer
remaining  available for  distribution  to Holders in  liquidation of the Issuer
after  satisfaction  of  liabilities  to  creditors of the Issuer as required by
applicable law (in either case, the "Liquidation Distribution").

         "Guarantee  Trustee"  means  JPMorgan  Chase  Bank,  until a  Successor
Guarantee Trustee has been appointed and has accepted such appointment  pursuant
to the  terms  of this  Guarantee  and  thereafter  means  each  such  Successor
Guarantee Trustee.

         "Holder"  means any holder,  as  registered on the books and records of
the Issuer, of any Capital Securities;  provided,  however, that, in determining
whether the holders of the requisite percentage of Capital Securities have given
any request, notice, consent or waiver hereunder, "Holder" shall not include the
Guarantor or any Affiliate of the Guarantor.

         "Indemnified  Person"  means the  Guarantee  Trustee  (including in its
individual  capacity),  any Affiliate of the Guarantee Trustee, or any officers,
directors,   shareholders,   members,  partners,   employees,   representatives,
nominees, custodians or agents of the Guarantee Trustee.

<PAGE> 6

         "Indenture"  means  the  Indenture,  dated as of  September  16,  2004,
between the Guarantor and JPMorgan Chase Bank,  not in its  individual  capacity
but solely as trustee, and any indenture  supplemental thereto pursuant to which
the Debentures are to be issued to the Institutional Trustee of the Issuer.

         "Liquidation  Distribution" has the meaning set forth in the definition
of "Guarantee Payments" herein.

         "Majority  in  liquidation  amount  of the  Capital  Securities"  means
Holder(s) of outstanding  Capital  Securities,  voting together as a class,  but
separately  from the  holders  of  Common  Securities,  of more  than 50% of the
aggregate  liquidation amount (including the stated amount that would be paid on
redemption,  liquidation or otherwise, plus accrued and unpaid Distributions to,
but excluding, the date upon which the voting percentages are determined) of all
Capital Securities then outstanding.

         "Obligations"  means  any  costs,  expenses  or  liabilities  (but  not
including liabilities related to taxes) of the Issuer, other than obligations of
the  Issuer to pay to  holders  of any Trust  Securities  the  amounts  due such
holders pursuant to the terms of the Trust Securities.

         "Officer's   Certificate"   means,   with  respect  to  any  Person,  a
certificate  signed by one  Authorized  Officer of such  Person.  Any  Officer's
Certificate  delivered  with respect to compliance  with a condition or covenant
provided for in this Guarantee shall include:

         (a) a statement that each officer signing the Officer's Certificate has
    read the covenant or condition and the definitions relating thereto;

         (b) a brief  statement  of the nature and scope of the  examination  or
    investigation   undertaken  by  each  officer  in  rendering  the  Officer's
    Certificate;

         (c) a statement  that each such  officer has made such  examination  or
    investigation  as, in such  officer's  opinion,  is necessary to enable such
    officer to express an informed opinion as to whether or not such covenant or
    condition has been complied with; and

         (d) a  statement  as to whether,  in the opinion of each such  officer,
    such condition or covenant has been complied with.

         "Person" means a legal person,  including any individual,  corporation,
estate, partnership,  joint venture,  association,  joint stock company, limited
liability  company,  trust,  unincorporated  association,  or  government or any
agency or political subdivision thereof, or any other entity of whatever nature.

         "Responsible Officer" means, with respect to the Guarantee Trustee, any
officer within the Corporate  Trust Office of the Guarantee  Trustee with direct
responsibility for the administration of any matters relating to this Guarantee,
including any vice president,  any assistant vice president,  any secretary, any
assistant secretary,  the treasurer,  any assistant treasurer, any trust officer
or  other  officer  of the  Corporate  Trust  Office  of the  Guarantee  Trustee
customarily  performing functions similar to those performed by any of the above
designated

                                      -3-

<PAGE> 7



officers and also means,  with respect to a particular  corporate  trust matter,
any other  officer to whom such  matter is  referred  because of that  officer's
knowledge of and familiarity with the particular subject.

         "Successor  Guarantee  Trustee"  means a  successor  Guarantee  Trustee
possessing the qualifications to act as Guarantee Trustee under Section 3.1.

         "Trust   Securities"  means  the  Common  Securities  and  the  Capital
Securities.

                                   ARTICLE II
               POWERS, DUTIES AND RIGHTS OF THE GUARANTEE TRUSTEE

SECTION 2.1.    Powers and Duties of the Guarantee Trustee.
                ------------------------------------------

                (a) This  Guarantee  shall be held by the Guarantee  Trustee for
         the benefit of the Holders of the Capital Securities, and the Guarantee
         Trustee shall not transfer this Guarantee to any Person except a Holder
         of Capital Securities  exercising his or her rights pursuant to Section
         4.4(b)  or to a  Successor  Guarantee  Trustee  on  acceptance  by such
         Successor  Guarantee  Trustee of its  appointment  to act as  Successor
         Guarantee  Trustee.  The right,  title and  interest  of the  Guarantee
         Trustee shall  automatically  vest in any Successor  Guarantee Trustee,
         and such vesting and  cessation of title shall be effective  whether or
         not conveyancing documents have been executed and delivered pursuant to
         the appointment of such Successor Guarantee Trustee.

                (b)   If an Event of  Default actually  known  to a  Responsible
         Officer of the Guarantee  Trustee has occurred and is  continuing,  the
         Guarantee  Trustee shall enforce this  Guarantee for the benefit of the
         Holders of the Capital Securities.

                (c) The Guarantee Trustee, before the occurrence of any Event of
         Default  and after the curing or waiving of all Events of Default  that
         may have occurred,  shall  undertake to perform only such duties as are
         specifically  set forth in this  Guarantee,  and no  implied  covenants
         shall be read into this  Guarantee  against the Guarantee  Trustee.  In
         case an Event of  Default  has  occurred  (that  has not been  cured or
         waived  pursuant  to  Section  2.4(b))  and  is  actually  known  to  a
         Responsible  Officer of the Guarantee  Trustee,  the Guarantee  Trustee
         shall  exercise  such of the  rights  and  powers  vested in it by this
         Guarantee,  and use the same  degree of care and skill in its  exercise
         thereof,   as  a  prudent  person  would  exercise  or  use  under  the
         circumstances in the conduct of his or her own affairs.

                (d) No provision of this Guarantee shall be construed to relieve
         the Guarantee Trustee from liability for its own negligent action,  its
         own  negligent  failure to act, or its own willful  misconduct,  except
         that:

                    (i)  prior to the  occurrence  of any Event of  Default  and
                after the curing or  waiving  of all Events of Default  that may
                have occurred:

                         (A) the duties and obligations of the Guarantee Trustee
                    shall be determined solely by the express provisions of this
                    Guarantee, and the

                                       -4-

<PAGE> 8


                    Guarantee  Trustee  shall  not  be  liable  except  for  the
                    performance   of  such   duties  and   obligations   as  are
                    specifically  set forth in this  Guarantee,  and no  implied
                    covenants or  obligations  shall be read into this Guarantee
                    against the Guarantee Trustee; and

                         (B) in the  absence  of bad  faith  on the  part of the
                    Guarantee  Trustee,  the Guarantee  Trustee may conclusively
                    rely, as to the truth of the statements and the  correctness
                    of the opinions expressed therein,  upon any certificates or
                    opinions  furnished to the Guarantee  Trustee and conforming
                    to the  requirements of this  Guarantee;  but in the case of
                    any such certificates or opinions furnished to the Guarantee
                    Trustee,  the  Guarantee  Trustee  shall  be under a duty to
                    examine the same to  determine  whether or not on their face
                    they conform to the requirements of this Guarantee;

                    (ii) the Guarantee Trustee shall not be liable for any error
                of judgment made in good faith by a  Responsible  Officer of the
                Guarantee   Trustee,   unless  it  shall  be  proved  that  such
                Responsible  Officer of the  Guarantee  Trustee or the Guarantee
                Trustee was negligent in  ascertaining  the pertinent facts upon
                which such judgment was made;

                    (iii) the Guarantee Trustee shall not be liable with respect
                to any  action  taken or omitted to be taken by it in good faith
                in accordance  with the written  direction of the Holders of not
                less  than a  Majority  in  liquidation  amount  of the  Capital
                Securities  relating to the time, method and place of conducting
                any  proceeding  for  any  remedy  available  to  the  Guarantee
                Trustee,  or exercising  any trust or power  conferred  upon the
                Guarantee Trustee under this Guarantee; and

                    (iv)  no  provision  of this  Guarantee  shall  require  the
                Guarantee  Trustee to expend or risk its own funds or  otherwise
                incur personal financial  liability in the performance of any of
                its duties or in the exercise of any of its rights or powers, if
                the  Guarantee   Trustee  shall  have  reasonable   grounds  for
                believing  that the  repayment  of such funds is not  reasonably
                assured to it under the terms of this Guarantee, or security and
                indemnity,  reasonably  satisfactory  to the Guarantee  Trustee,
                against such risk or liability is not reasonably assured to it.

SECTION 2.2.    Certain Rights of the Guarantee Trustee.
                ---------------------------------------

                (a) Subject to the provisions of Section 2.1:

                    (i) The Guarantee  Trustee may conclusively  rely, and shall
                be fully protected in acting or refraining from acting upon, any
                resolution, certificate, statement, instrument, opinion, report,
                notice,  request,  direction,  consent,  order, bond, debenture,
                note,  other evidence of indebtedness or other paper or document
                believed  by it to be genuine and to have been  signed,  sent or
                presented by the proper party or parties.

                    (ii) Any direction or act of the Guarantor  contemplated  by
                this Guarantee shall be  sufficiently  evidenced by an Officer's
                Certificate.


                                       -5-

<PAGE> 9

                    (iii) Whenever, in the administration of this Guarantee, the
                Guarantee  Trustee  shall  deem it  desirable  that a matter  be
                proved or established  before taking,  suffering or omitting any
                action  hereunder,  the Guarantee Trustee (unless other evidence
                is herein  specifically  prescribed)  may, in the absence of bad
                faith  on its  part,  request  and  conclusively  rely  upon  an
                Officer's  Certificate of the Guarantor  which,  upon receipt of
                such request, shall be promptly delivered by the Guarantor.

                    (iv) The Guarantee  Trustee shall have no duty to see to any
                recording,  filing or  registration  of any  instrument or other
                writing  (or  any   rerecording,   refiling  or   reregistration
                thereof).

                    (v) The  Guarantee  Trustee may consult  with counsel of its
                selection,  and the  advice  or  opinion  of such  counsel  with
                respect   to  legal   matters   shall   be  full  and   complete
                authorization  and  protection  in respect of any action  taken,
                suffered  or  omitted  by it  hereunder  in  good  faith  and in
                accordance  with such  advice or  opinion.  Such  counsel may be
                counsel  to the  Guarantor  or any of  its  Affiliates  and  may
                include any of its employees.  The Guarantee  Trustee shall have
                the  right  at any  time to  seek  instructions  concerning  the
                administration  of this  Guarantee  from any court of  competent
                jurisdiction.

                    (vi) The  Guarantee  Trustee shall be under no obligation to
                exercise  any of the  rights  or  powers  vested  in it by  this
                Guarantee at the request or direction of any Holder, unless such
                Holder  shall  have  provided  to  the  Guarantee  Trustee  such
                security and indemnity, reasonably satisfactory to the Guarantee
                Trustee,  against the costs, expenses (including attorneys' fees
                and expenses and the expenses of the Guarantee Trustee's agents,
                nominees or custodians) and  liabilities  that might be incurred
                by it in  complying  with such request or  direction,  including
                such  reasonable  advances as may be requested by the  Guarantee
                Trustee;  provided,  however,  that  nothing  contained  in this
                Section  2.2(a)(vi)  shall  be taken to  relieve  the  Guarantee
                Trustee,  upon the  occurrence  of an Event of  Default,  of its
                obligation  to  exercise  the rights and powers  vested in it by
                this Guarantee.

                    (vii) The  Guarantee  Trustee shall not be bound to make any
                investigation   into  the  facts  or   matters   stated  in  any
                resolution, certificate, statement, instrument, opinion, report,
                notice,  request,  direction,  consent,  order, bond, debenture,
                note, other evidence of indebtedness or other paper or document,
                but the  Guarantee  Trustee,  in its  discretion,  may make such
                further inquiry or  investigation  into such facts or matters as
                it may see fit.

                    (viii) The  Guarantee  Trustee may execute any of the trusts
                or powers  hereunder  or  perform  any duties  hereunder  either
                directly  or by  or  through  agents,  nominees,  custodians  or
                attorneys,  and the Guarantee  Trustee shall not be  responsible
                for any  misconduct  or  negligence  on the part of any agent or
                attorney appointed with due care by it hereunder.

                                      -6-

<PAGE> 10


                    (ix) Any action taken by the Guarantee Trustee or its agents
                hereunder shall bind the Holders of the Capital Securities,  and
                the signature of the Guarantee Trustee or its agents alone shall
                be sufficient and effective to perform any such action. No third
                party shall be required  to inquire as to the  authority  of the
                Guarantee  Trustee to so act or as to its compliance with any of
                the terms and provisions of this Guarantee,  both of which shall
                be  conclusively  evidenced  by the  Guarantee  Trustee's or its
                agent's taking such action.

                    (x) Whenever in the  administration  of this  Guarantee  the
                Guarantee   Trustee   shall   deem  it   desirable   to  receive
                instructions  with respect to  enforcing  any remedy or right or
                taking any other action hereunder, the Guarantee Trustee (A) may
                request   instructions   from  the  Holders  of  a  Majority  in
                liquidation  amount of the Capital  Securities,  (B) may refrain
                from  enforcing such remedy or right or taking such other action
                until such  instructions are received and (C) shall be protected
                in  conclusively  relying on or acting in  accordance  with such
                instructions.

                    (xi) The  Guarantee  Trustee  shall  not be  liable  for any
                action  taken,  suffered,  or  omitted to be taken by it in good
                faith and  reasonably  believed by it to be authorized or within
                the  discretion  or rights or powers  conferred  upon it by this
                Guarantee.

                (b) No provision of this Guarantee shall be deemed to impose any
          duty or obligation on the Guarantee Trustee to perform any act or acts
          or exercise any right, power, duty or obligation  conferred or imposed
          on it, in any  jurisdiction  in which it shall be  illegal or in which
          the  Guarantee   Trustee  shall  be   unqualified  or  incompetent  in
          accordance  with  applicable law to perform any such act or acts or to
          exercise any such right,  power,  duty or  obligation.  No  permissive
          power  or  authority  available  to the  Guarantee  Trustee  shall  be
          construed to be a duty.

SECTION 2.3.    Not Responsible for Recitals or Issuance of Guarantee.
                -----------------------------------------------------

                The recitals  contained in this Guarantee  shall be taken as the
statements  of the  Guarantor,  and the  Guarantee  Trustee  does not assume any
responsibility   for  their   correctness.   The  Guarantee   Trustee  makes  no
representation as to the validity or sufficiency of this Guarantee.

SECTION 2.4.    Events of Default; Waiver.
                -------------------------

                (a) An Event of Default under this Guarantee will occur upon the
          failure  of the  Guarantor  to  perform  any of its  payment  or other
          obligations hereunder.

                (b) The  Holders  of a  Majority  in  liquidation  amount of the
          Capital  Securities may, voting or consenting as a class, on behalf of
          the Holders of all of the Capital Securities,  waive any past Event of
          Default  and its  consequences.  Upon such  waiver,  any such Event of
          Default shall cease to exist,  and shall be deemed to have been cured,
          for every purpose of this  Guarantee,  but no such waiver shall extend
          to any  subsequent  or other default or Event of Default or impair any
          right consequent thereon.

                                      -7-

<PAGE> 11


SECTION 2.5.    Events of Default; Notice.
                -------------------------

                (a) The  Guarantee  Trustee  shall,  within  90 days  after  the
          occurrence  of an Event of  Default,  transmit  by mail,  first  class
          postage prepaid, to the Holders of the Capital Securities,  notices of
          all Events of Default  actually known to a Responsible  Officer of the
          Guarantee  Trustee,  unless such  defaults  have been cured before the
          giving of such notice;  provided,  however, that the Guarantee Trustee
          shall be  protected  in  withholding  such  notice if and so long as a
          Responsible  Officer of the Guarantee Trustee in good faith determines
          that the withholding of such notice is in the interests of the Holders
          of the Capital Securities.

                (b) The Guarantee Trustee shall not be charged with knowledge of
          any Event of Default unless the Guarantee  Trustee shall have received
          written  notice  thereof from the Guarantor or a Holder of the Capital
          Securities,  or a Responsible Officer of the Guarantee Trustee charged
          with the  administration of this Guarantee shall have actual knowledge
          thereof.

                                  ARTICLE III
                              THE GUARANTEE TRUSTEE

SECTION 3.1.    The Guarantee Trustee; Eligibility.
                ----------------------------------

                (a) There shall at all times be a Guarantee Trustee which shall:

                    (i) not be an Affiliate of the Guarantor; and

                    (ii) be a corporation or national association  organized and
                doing business under the laws of the United States of America or
                any state or  territory  thereof or of the District of Columbia,
                or Person authorized under such laws to exercise corporate trust
                powers,  having a combined capital and surplus of at least Fifty
                Million U.S. Dollars  ($50,000,000),  and subject to supervision
                or  examination  by federal,  state,  territorial or District of
                Columbia authority.  If such corporation or national association
                publishes  reports of condition at least  annually,  pursuant to
                law  or to the  requirements  of the  supervising  or  examining
                authority  referred  to above,  then,  for the  purposes of this
                Section  3.1(a)(ii),  the  combined  capital and surplus of such
                corporation  or national  association  shall be deemed to be its
                combined  capital  and  surplus as set forth in its most  recent
                report of condition so published.

                (b) If at any  time  the  Guarantee  Trustee  shall  cease to be
          eligible to so act under Section 3.1(a),  the Guarantee  Trustee shall
          immediately  resign in the  manner  and with the  effect  set forth in
          Section 3.2(c).

                (c)  If  the   Guarantee   Trustee  has  or  shall  acquire  any
          "conflicting  interest'  within the  meaning of Section  310(b) of the
          Trust Indenture Act, the Guarantee Trustee shall either eliminate such
          interest  or resign to the extent and in the manner  provided  by, and
          subject to, this Guarantee.


                                      -8-

<PAGE> 12

SECTION 3.2.    Appointment, Removal and Resignation of the Guarantee Trustee.
                -------------------------------------------------------------

                (a)  Subject to Section  3.2(b),  the  Guarantee  Trustee may be
          appointed or removed without cause at any time by the Guarantor except
          during an Event of Default.

                (b) The  Guarantee  Trustee  shall not be removed in  accordance
          with  Section  3.2(a)  until a  Successor  Guarantee  Trustee has been
          appointed  and has accepted  such  appointment  by written  instrument
          executed by such  Successor  Guarantee  Trustee and  delivered  to the
          Guarantor.

                (c) The Guarantee  Trustee appointed to office shall hold office
          until a Successor Guarantee Trustee shall have been appointed or until
          its  removal or  resignation.  The  Guarantee  Trustee may resign from
          office  (without  need  for  prior  or  subsequent  accounting)  by an
          instrument in writing executed by the Guarantee  Trustee and delivered
          to the  Guarantor,  which  resignation  shall not take effect  until a
          Successor  Guarantee  Trustee has been appointed and has accepted such
          appointment  by an  instrument in writing  executed by such  Successor
          Guarantee  Trustee and  delivered to the  Guarantor  and the resigning
          Guarantee Trustee.

                (d) If no Successor  Guarantee Trustee shall have been appointed
          and  accepted  appointment  as provided in this  Section 3.2 within 60
          days after  delivery of an instrument of removal or  resignation,  the
          Guarantee Trustee resigning or being removed may petition any court of
          competent  jurisdiction  for  appointment  of  a  Successor  Guarantee
          Trustee.  Such court may thereupon,  after prescribing such notice, if
          any, as it may deem proper, appoint a Successor Guarantee Trustee.

                (e) No  Guarantee  Trustee  shall  be  liable  for  the  acts or
          omissions to act of any Successor Guarantee Trustee.

                (f) Upon termination of this Guarantee or removal or resignation
          of the Guarantee  Trustee  pursuant to this Section 3.2, the Guarantor
          shall pay to the Guarantee  Trustee all amounts owing to the Guarantee
          Trustee  under  Sections  7.2  and  7.3  accrued  to the  date of such
          termination, removal or resignation.


                                   ARTICLE IV
                                    GUARANTEE

SECTION 4.1.    Guarantee.
                ---------

                (a) The Guarantor irrevocably and unconditionally  agrees to pay
          in full to the Holders the Guarantee Payments (without  duplication of
          amounts  theretofore paid by the Issuer),  as and when due, regardless
          of any defense (except as defense of payment by the Issuer),  right of
          set-off  or  counterclaim  that the  Issuer  may have or  assert.  The
          Guarantor's obligation to make a Guarantee Payment may be satisfied by
          direct payment of the required amounts by the Guarantor to the Holders
          or by causing the Issuer to pay such amounts to the Holders.


                                      -9-

<PAGE> 13

                (b) The  Guarantor  hereby  also  agrees to  assume  any and all
          Obligations of the Issuer and in the event any such  Obligation is not
          so assumed,  subject to the terms and conditions hereof, the Guarantor
          hereby irrevocably and unconditionally  guarantees to each Beneficiary
          the full payment,  when and as due, of any and all Obligations to such
          Beneficiaries.  This Guarantee is intended to be for the Beneficiaries
          who have received notice hereof.

SECTION 4.2.    Waiver of Notice and Demand.
                ---------------------------

                The  Guarantor  hereby  waives  notice  of  acceptance  of  this
Guarantee  and of any  liability to which it applies or may apply,  presentment,
demand for payment,  any right to require a proceeding  first against the Issuer
or any other Person before proceeding against the Guarantor,  protest, notice of
nonpayment,  notice of dishonor,  notice of redemption and all other notices and
demands.

SECTION 4.3.    Obligations Not Affected.
                ------------------------

                The  obligations,   covenants,  agreements  and  duties  of  the
Guarantor under this Guarantee shall in no way be affected or impaired by reason
of the happening from time to time of any of the following:

                (a) the release or waiver, by operation of law or otherwise,  of
          the  performance or observance by the Issuer of any express or implied
          agreement,  covenant,  term  or  condition  relating  to  the  Capital
          Securities to be performed or observed by the Issuer;

                (b) the  extension  of time for the payment by the Issuer of all
          or  any  portion  of  the  Distributions,  Redemption  Price,  Special
          Redemption Price,  Liquidation  Distribution or any other sums payable
          under the terms of the Capital Securities or the extension of time for
          the performance of any other obligation  under,  arising out of, or in
          connection  with, the Capital  Securities  (other than an extension of
          time for the payment of the Distributions,  Redemption Price,  Special
          Redemption Price,  Liquidation Distribution or other sums payable that
          results  from the  extension  of any  interest  payment  period on the
          Debentures  or any  extension of the maturity  date of the  Debentures
          permitted by the Indenture);

                (c) any  failure,  omission,  delay or lack of  diligence on the
          part  of the  Holders  to  enforce,  assert  or  exercise  any  right,
          privilege,  power or remedy  conferred on the Holders  pursuant to the
          terms of the  Capital  Securities,  or any  action  on the part of the
          Issuer granting indulgence or extension of any kind;

                (d) the voluntary or involuntary liquidation,  dissolution, sale
          of any collateral,  receivership,  insolvency,  bankruptcy, assignment
          for the benefit of creditors, reorganization, arrangement, composition
          or  readjustment of debt of, or other similar  proceedings  affecting,
          the Issuer or any of the assets of the Issuer;

                (e) any  invalidity  of, or defect or deficiency in, the Capital
          Securities;


                                      -10-

<PAGE> 14

                (f) the  settlement or compromise of any  obligation  guaranteed
          hereby or hereby incurred; or

                (g) any  other  circumstance  whatsoever  that  might  otherwise
          constitute a legal or  equitable  discharge or defense of a guarantor,
          it being the intent of this  Section 4.3 that the  obligations  of the
          Guarantor  hereunder shall be absolute and unconditional under any and
          all circumstances.

                There shall be no  obligation  of the Holders to give notice to,
or obtain  consent of, the Guarantor with respect to the happening of any of the
foregoing.

SECTION 4.4.    Rights of Holders.
                -----------------

                (a) The  Holders  of a  Majority  in  liquidation  amount of the
          Capital Securities have the right to direct the time, method and place
          of conducting any proceeding for any remedy available to the Guarantee
          Trustee in respect of this  Guarantee or to direct the exercise of any
          trust or  power  conferred  upon  the  Guarantee  Trustee  under  this
          Guarantee;  provided,  however, that (subject to Sections 2.1 and 2.2)
          the  Guarantee  Trustee  shall have the right to decline to follow any
          such  direction if the  Guarantee  Trustee  shall  determine  that the
          actions so directed  would be unjustly  prejudicial to the Holders not
          taking  part in  such  direction  or if the  Guarantee  Trustee  being
          advised by legal counsel  determines  that the action or proceeding so
          directed may not lawfully be taken or if the Guarantee Trustee in good
          faith by its board of directors or trustees,  executive committee or a
          trust committee of directors or trustees and/or  Responsible  Officers
          shall  determine  that the  action or  proceeding  so  directed  would
          involve the Guarantee Trustee in personal liability.

                (b) Any  Holder of  Capital  Securities  may  institute  a legal
          proceeding  directly  against the  Guarantor to enforce the  Guarantee
          Trustee's  rights under this  Guarantee,  without first  instituting a
          legal  proceeding  against the Issuer,  the  Guarantee  Trustee or any
          other Person. The Guarantor waives any right or remedy to require that
          any such action be brought  first  against the Issuer,  the  Guarantee
          Trustee or any other Person before so proceeding  directly against the
          Guarantor.

SECTION 4.5.    Guarantee of Payment.
                --------------------

                This  Guarantee  creates  a  guarantee  of  payment  and  not of
          collection.

SECTION 4.6.    Subrogation.
                -----------

                The Guarantor  shall be subrogated to all (if any) rights of the
Holders of Capital  Securities against the Issuer in respect of any amounts paid
to such Holders by the Guarantor under this Guarantee;  provided,  however, that
the Guarantor shall not (except to the extent required by applicable  provisions
of law) be entitled to enforce or exercise  any right that it may acquire by way
of subrogation or any indemnity,  reimbursement or other agreement, in all cases
as a result of payment under this Guarantee, if, after giving effect to any such
payment,  any amounts  are due and unpaid  under this  Guarantee.  If any amount
shall be paid to the  Guarantor

                                      -11-

<PAGE> 15

in violation of the preceding sentence, the Guarantor agrees to hold such amount
in trust for the Holders and to pay over such amount to the Holders.

SECTION 4.7.    Independent Obligations.
                -----------------------

                The Guarantor  acknowledges  that its obligations  hereunder are
independent  of the  obligations  of the  Issuer  with  respect  to the  Capital
Securities  and that the  Guarantor  shall be liable as principal  and as debtor
hereunder to make  Guarantee  Payments  pursuant to the terms of this  Guarantee
notwithstanding  the  occurrence  of any event  referred to in  subsections  (a)
through (g), inclusive, of Section 4.3 hereof.

SECTION 4.8.    Enforcement.
                -----------

                A  Beneficiary  may enforce  the  Obligations  of the  Guarantor
contained in Section 4.1(b)  directly  against the Guarantor,  and the Guarantor
waives any right or remedy to require  that any  action be brought  against  the
Issuer or any other person or entity before proceeding against the Guarantor.

                The Guarantor  shall be subrogated to all rights (if any) of any
Beneficiary   against  the  Issuer  in  respect  of  any  amounts  paid  to  the
Beneficiaries by the Guarantor under this Guarantee; provided, however, that the
Guarantor shall not (except to the extent  required by applicable  provisions of
law) be entitled to enforce or exercise any rights that it may acquire by way of
subrogation or any indemnity,  reimbursement or other agreement, in all cases as
a result of payment  under  this  Guarantee,  if,  after  giving  effect to such
payment, any amounts are due and unpaid under this Guarantee.

                                   ARTICLE V
                    LIMITATION OF TRANSACTIONS; SUBORDINATION

SECTION 5.1.    Limitation of Transactions.
                --------------------------

                So long as any Capital  Securities  remain  outstanding,  if (a)
there  shall  have  occurred  and be  continuing  an Event of Default or (b) the
Guarantor shall have selected an Extension Period as provided in the Declaration
and  such  period,  or  any  extension  thereof,  shall  have  commenced  and be
continuing,  then the  Guarantor  may not (x)  declare or pay any  dividends  or
distributions on, or redeem,  purchase,  acquire,  or make a liquidation payment
with respect to, any of the Guarantor's capital stock or (y) make any payment of
principal of or interest or premium,  if any, on or repay,  repurchase or redeem
any debt  securities of the Guarantor  that rank pari passu in all respects with
or junior in interest to the  Debentures  (other  than (i)  payments  under this
Guarantee,  (ii)  repurchases,  redemptions or other  acquisitions  of shares of
capital stock of the Guarantor (A) in connection  with any employment  contract,
benefit plan or other similar arrangement with or for the benefit of one or more
employees,  officers,  directors,  or  consultants,  (B)  in  connection  with a
dividend  reinvestment  or stockholder  stock purchase plan or (C) in connection
with the issuance of capital stock of the Guarantor (or  securities  convertible
into or exercisable for such capital stock),  as consideration in an acquisition
transaction  entered into prior to the occurrence of the Event of Default or the
applicable   Extension   Period,   (iii)   as  a   result   of   any   exchange,
reclassification,  combination  or  conversion  of any  class or  series  of the
Guarantor's  capital  stock  (or  any  capital  stock  of a

                                      -12-

<PAGE> 16



subsidiary of the Guarantor) for any class or series of the Guarantor's  capital
stock or of any class or series of the Guarantor's indebtedness for any class or
series  of the  Guarantor's  capital  stock,  (iv) the  purchase  of  fractional
interests in shares of the Guarantor's  capital stock pursuant to the conversion
or exchange  provisions of such capital stock or the security being converted or
exchanged,   (v)  any   declaration  of  a  dividend  in  connection   with  any
stockholder's  rights plan, or the issuance of rights,  stock or other  property
under any  stockholder's  rights plan, or the redemption or repurchase of rights
pursuant thereto, or (vi) any dividend in the form of stock,  warrants,  options
or other rights where the dividend  stock or the stock issuable upon exercise of
such  warrants,  options or other  rights is the same stock as that on which the
dividend is being paid or ranks pari passu with or junior to such stock).

SECTION 5.2.    Ranking.
                -------

                This  Guarantee will  constitute an unsecured  obligation of the
Guarantor  and will  rank  subordinate  and  junior in right of  payment  to all
present and future  Senior  Indebtedness  (as defined in the  Indenture)  of the
Guarantor. By their acceptance thereof, each Holder of Capital Securities agrees
to the  foregoing  provisions  of this  Guarantee  and the other terms set forth
herein.

                The right of the Guarantor to participate in any distribution of
assets of any of its  subsidiaries  upon any such  subsidiary's  liquidation  or
reorganization  or otherwise is subject to the prior claims of creditors of that
subsidiary,  except to the extent the  Guarantor  may itself be  recognized as a
creditor of that subsidiary. Accordingly, the Guarantor's obligations under this
Guarantee  will  be  effectively   subordinated   to  all  existing  and  future
liabilities of the Guarantor's  subsidiaries,  and claimants should look only to
the assets of the Guarantor for payments  thereunder.  This  Guarantee  does not
limit the  incurrence  or issuance  of other  secured or  unsecured  debt of the
Guarantor,  including Senior Indebtedness of the Guarantor,  under any indenture
or agreement that the Guarantor may enter into in the future or otherwise.

                                   ARTICLE VI
                                   TERMINATION

SECTION 6.1.    Termination.
                -----------

                This Guarantee shall terminate as to the Capital  Securities (i)
upon full payment of the Redemption  Price or the Special  Redemption  Price, as
the case may be,  of all  Capital  Securities  then  outstanding,  (ii) upon the
distribution  of all of the  Debentures  to the  Holders  of all of the  Capital
Securities or (iii) upon full payment of the amounts  payable in accordance with
the Declaration upon dissolution of the Issuer.  This Guarantee will continue to
be  effective  or will be  reinstated,  as the case  may be,  if at any time any
Holder of Capital  Securities  must  restore  payment of any sums paid under the
Capital Securities or under this Guarantee.


                                      -13-

<PAGE> 17

                                  ARTICLE VII
                                 INDEMNIFICATION

SECTION 7.1.    Exculpation.
                -----------

                (a) No  Indemnified  Person  shall  be  liable,  responsible  or
          accountable  in damages or otherwise  to the  Guarantor or any Covered
          Person for any loss,  damage or claim incurred by reason of any act or
          omission of such  Indemnified  Person in good faith in accordance with
          this Guarantee and in a manner that such Indemnified Person reasonably
          believed  to be within the scope of the  authority  conferred  on such
          Indemnified  Person  by  this  Guarantee  or by  law,  except  that an
          Indemnified  Person shall be liable for any such loss, damage or claim
          incurred by reason of such Indemnified  Person's negligence or willful
          misconduct with respect to such acts or omissions.

                (b) An Indemnified Person shall be fully protected in relying in
          good faith upon the  records of the Issuer or the  Guarantor  and upon
          such  information,  opinions,  reports or statements  presented to the
          Issuer or the  Guarantor  by any Person as to matters the  Indemnified
          Person reasonably believes are within such other Person's professional
          or expert competence and who, if selected by such Indemnified  Person,
          has been selected with  reasonable  care by such  Indemnified  Person,
          including information, opinions, reports or statements as to the value
          and amount of the assets,  liabilities,  profits, losses, or any other
          facts  pertinent  to the  existence  and  amount of assets  from which
          Distributions to Holders of Capital Securities might properly be paid.

SECTION 7.2.    Indemnification.
                ---------------

                (a) The Guarantor  agrees to indemnify each  Indemnified  Person
          for, and to hold each Indemnified Person harmless against, any and all
          loss, liability,  damage, claim or expense incurred without negligence
          or willful misconduct on the part of the Indemnified  Person,  arising
          out of or in connection with the acceptance or  administration  of the
          trust or trusts hereunder,  including but not limited to the costs and
          expenses  (including  reasonable  legal  fees  and  expenses)  of  the
          Indemnified  Person defending itself against,  or  investigating,  any
          claim or liability in connection  with the exercise or  performance of
          any of the  Indemnified  Person's  powers  or  duties  hereunder.  The
          obligation to indemnify as set forth in this Section 7.2 shall survive
          the   resignation  or  removal  of  the  Guarantee   Trustee  and  the
          termination of this Guarantee.

                (b) Promptly after receipt by an  Indemnified  Person under this
          Section  7.2  of  notice  of the  commencement  of  any  action,  such
          Indemnified  Person will, if a claim in respect  thereof is to be made
          against the Guarantor  under this Section 7.2, notify the Guarantor in
          writing of the commencement  thereof; but the failure so to notify the
          Guarantor  (i) will not relieve the  Guarantor  from  liability  under
          paragraph  (a) above unless and to the extent that the  Guarantor  did
          not  otherwise  learn of such action and such  failure  results in the
          forfeiture  by the  Guarantor of  substantial  rights and defenses and
          (ii)  will  not,  in  any  event,   relieve  the  Guarantor  from  any
          obligations to any Indemnified  Person other than the  indemnification
          obligation  provided in paragraph (a) above.  The  Guarantor  shall be
          entitled  to  appoint  counsel  of  the  Guarantor's   choice  at  the
          Guarantor's

                                      -14-
<PAGE> 18



          expense to represent  the  Indemnified  Person in any action for which
          indemnification  is sought  (in  which  case the  Guarantor  shall not
          thereafter  be  responsible  for the fees and expenses of any separate
          counsel  retained by the  Indemnified  Person or Persons except as set
          forth  below);   provided,   however,   that  such  counsel  shall  be
          satisfactory   to  the   Indemnified   Person.   Notwithstanding   the
          Guarantor's  election to appoint  counsel to represent the Indemnified
          Person in any action,  the Indemnified  Person shall have the right to
          employ separate counsel  (including local counsel),  and the Guarantor
          shall bear the  reasonable  fees,  costs and expenses of such separate
          counsel (and local  counsel),  if (i) the use of counsel chosen by the
          Guarantor  to represent  the  Indemnified  Person  would  present such
          counsel  with a conflict  of  interest,  (ii) the actual or  potential
          defendants  in,  or  targets  of,  any such  action  include  both the
          Indemnified  Person and the Guarantor and the Indemnified Person shall
          have reasonably  concluded that there may be legal defenses  available
          to it and/or other  Indemnified  Persons which are  different  from or
          additional to those  available to the  Guarantor,  (iii) the Guarantor
          shall not have employed counsel satisfactory to the Indemnified Person
          to represent the  Indemnified  Person  within a reasonable  time after
          notice of the  institution of such action or (iv) the Guarantor  shall
          authorize the  Indemnified  Person to employ  separate  counsel at the
          expense of the Guarantor.  The Guarantor  will not,  without the prior
          written  consent of the Indemnified  Persons,  settle or compromise or
          consent to the entry of any  judgment  with  respect to any pending or
          threatened  claim,  action,  suit or  proceeding  in  respect of which
          indemnification  or contribution may be sought  hereunder  (whether or
          not the  Indemnified  Persons are actual or potential  parties to such
          claim  or  action)  unless  such  settlement,  compromise  or  consent
          includes an unconditional  release of each Indemnified Person from all
          liability arising out of such claim, action, suit or proceeding.

SECTION 7.3.    Compensation; Reimbursement of Expenses.
                ---------------------------------------

                Other  than as  provided  in the  Fee  Agreement  of  even  date
herewith  between  Cohen Bros.  & Company,  the  Guarantee  Trustee and Delaware
Trustee (as defined in the Declaration), the Guarantor agrees:

                (a) to pay to the  Guarantee  Trustee  from  time to  time  such
          compensation for all services  rendered by it hereunder as the parties
          shall  agree to from  time to time  (which  compensation  shall not be
          limited by any  provision  of law in regard to the  compensation  of a
          trustee of an express trust); and

                (b) except as otherwise  expressly provided herein, to reimburse
          the  Guarantee  Trustee  upon  request  for all  reasonable  expenses,
          disbursements  and advances  incurred or made by it in accordance with
          any provision of this Guarantee (including the reasonable compensation
          and the expenses and disbursements of its agents and counsel),  except
          any such expense,  disbursement  or advance as may be  attributable to
          its negligence or willful misconduct.

                The provisions of this Section 7.3 shall survive the resignation
or removal of the Guarantee Trustee and the termination of this Guarantee.


                                      -15-

<PAGE> 19

                                  ARTICLE VIII
                                  MISCELLANEOUS

SECTION 8.1.    Successors and Assigns.
                ----------------------

                All guarantees and agreements  contained in this Guarantee shall
bind the successors,  assigns,  receivers,  trustees and  representatives of the
Guarantor  and  shall  inure  to the  benefit  of  the  Holders  of the  Capital
Securities   then   outstanding.   Except  in  connection  with  any  merger  or
consolidation of the Guarantor with or into another entity or any sale, transfer
or lease of the Guarantor's  assets or capital stock to another entity,  in each
case to the extent  permitted under the Indenture,  the Guarantor may not assign
its rights or delegate its  obligations  under this Guarantee  without the prior
approval of the Holders of not less than a Majority in liquidation amount of the
Capital Securities.

SECTION 8.2.    Amendments.
                ----------

                Except with respect to any changes that do not adversely  affect
the rights of Holders of the  Capital  Securities  in any  material  respect (in
which case no  consent  of Holders  will be  required),  this  Guarantee  may be
amended only with the prior  approval of the Holders of not less than a Majority
in  liquidation  amount  of  the  Capital  Securities.  The  provisions  of  the
Declaration with respect to amendments  thereof shall apply equally with respect
to amendments of the Guarantee.

SECTION 8.3.    Notices.
                -------

                All notices  provided for in this Guarantee shall be in writing,
duly signed by the party giving such notice, and shall be delivered,  telecopied
or mailed by first class mail, as follows:

                (a)  If  given  to  the  Guarantee  Trustee,  at  the  Guarantee
          Trustee's  mailing  address set forth below (or such other  address as
          the Guarantee Trustee may give notice of to the Holders of the Capital
          Securities):

                           JPMorgan Chase Bank
                           600 Travis Street, 50th Floor
                           Houston, Texas 77002
                           Attention:  Institutional Trust Services
                           Central Bancorp Capital Trust I
                           Telecopy:  (713) 216-2101
                           Telephone: (713) 216-4181

                (b) If  given  to the  Guarantor,  at  the  Guarantor's  mailing
          address set forth below (or such other  address as the  Guarantor  may
          give  notice of to the Holders of the  Capital  Securities  and to the
          Guarantee Trustee):


                                      -16-

<PAGE> 20

                           Central Bancorp, Inc.
                           399 Highland Avenue
                           Somerville, Massachusetts 02144
                           Attention: Michael K. Devlin
                           Telecopy: (617) 629-4391
                           Telephone: (617) 528-4000

                (c) If given to any  Holder of the  Capital  Securities,  at the
          address set forth on the books and records of the Issuer.

                All such  notices  shall  be  deemed  to have  been  given  when
received in person,  telecopied with receipt confirmed, or mailed by first class
mail,  postage  prepaid,  except  that if a notice or other  document is refused
delivery or cannot be delivered  because of a changed address of which no notice
was given,  such notice or other document shall be deemed to have been delivered
on the date of such refusal or inability to deliver.

SECTION 8.4.    Benefit.
                -------

                This  Guarantee  is solely for the benefit of the Holders of the
Capital   Securities  and,   subject  to  Section  2.1(a),   is  not  separately
transferable from the Capital Securities.

SECTION 8.5.    Governing Law.
                -------------

                THIS GUARANTEE SHALL BE GOVERNED BY, AND CONSTRUED IN ACCORDANCE
WITH,  THE LAW OF THE STATE OF NEW YORK,  WITHOUT  REGARD  TO  CONFLICT  OF LAWS
PRINCIPLES THEREOF.

SECTION 8.6.    Counterparts.
                ------------

                This  Guarantee  may contain  more than one  counterpart  of the
signature  page  and this  Guarantee  may be  executed  by the  affixing  of the
signature of the Guarantor and the Guarantee  Trustee to any of such counterpart
signature pages. All of such counterpart signature pages shall be read as though
one,  and they shall have the same force and effect as though all of the signers
had signed a single signature page.

                                      -17-

<PAGE> 21


                THIS  GUARANTEE  is  executed as of the day and year first above
written.


                                               CENTRAL BANCORP, INC.,
                                               as Guarantor


                                               By: /s/ John D. Doherty
                                               Name:  John D. Doherty
                                               Title: Chairman, President and
                                                      Chief Executive Officer


                                               JPMORGAN CHASE BANK, as Guarantee
                                               Trustee


                                               By: /s/ Maria D. Calzado
                                               Name:  Maria D. Calzado
                                               Title: Vice President


                                      -18-