<PAGE>

                                                                    EXHIBIT 4.21

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                              GUARANTEE AGREEMENT

                                     Between

                              The Chubb Corporation
                                 (as Guarantor)

                                       and

                          Bank One Trust Company, N.A.
                                  (as Trustee)

                             dated as of       , 20

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                                TABLE OF CONTENTS

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                                    ARTICLE I
DEFINITIONS.......................................................................................................   1

   SECTION 1.1  Definitions.......................................................................................   1

                                   ARTICLE II
TRUST INDENTURE ACT...............................................................................................   5

   SECTION 2.1  Trust Indenture Act; Application..................................................................   5
   SECTION 2.2  List of Holders...................................................................................   5
   SECTION 2.3  Reports by the Guarantee Trustee..................................................................   5
   SECTION 2.4  Periodic Reports to Guarantee Trustee.............................................................   5
   SECTION 2.5  Evidence of Compliance with Conditions Precedent..................................................   6
   SECTION 2.6  Events of Default; Waiver.........................................................................   6
   SECTION 2.7  Event of Default; Notice..........................................................................   6
   SECTION 2.8  Conflicting Interests.............................................................................   6

                                   ARTICLE III
POWERS, DUTIES AND RIGHTS OF THE GUARANTEE TRUSTEE................................................................   7

   SECTION 3.1  Powers and Duties of the Guarantee Trustee........................................................   7
   SECTION 3.2  Certain Rights of Guarantee Trustee...............................................................   8
   SECTION 3.3  Indemnity.........................................................................................  10

                                   ARTICLE IV
GUARANTEE TRUSTEE................................................................................................   10

   SECTION 4.1  Guarantee Trustee; Eligibility...................................................................   10
   SECTION 4.2  Appointment, Removal and Resignation of the Guarantee Trustee....................................   11

                                    ARTICLE V
GUARANTEE........................................................................................................   12

   SECTION 5.1  Guarantee........................................................................................   12
   SECTION 5.2  Waiver of Notice and Demand......................................................................   12
   SECTION 5.3  Obligations Not Affected.........................................................................   12
   SECTION 5.4  Rights of Holders................................................................................   13
   SECTION 5.5  Guarantee of Payment.............................................................................   13
   SECTION 5.6  Subrogation......................................................................................   14
   SECTION 5.7  Independent Obligations..........................................................................   14
</TABLE>

                                       i

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                               Table of Contents
                                  (continued)

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                                   ARTICLE VI
COVENANTS AND SUBORDINATION......................................................................................   14

   SECTION 6.1  Subordination....................................................................................   14
   SECTION 6.2  Pari Passu Guarantees............................................................................   14

                                   ARTICLE VII
TERMINATION......................................................................................................   15

   SECTION 7.1  Termination......................................................................................   15

                                  ARTICLE VIII
MISCELLANEOUS....................................................................................................   15

   SECTION 8.1  Successors and Assigns...........................................................................   15
   SECTION 8.2  Amendments.......................................................................................   15
   SECTION 8.3  Notices..........................................................................................   16
   SECTION 8.4  Benefit..........................................................................................   17
   SECTION 8.5  Interpretation...................................................................................   17
   SECTION 8.6  GOVERNING LAW....................................................................................   17
   SECTION 8.7  Counterparts.....................................................................................   18
</TABLE>

                                       ii

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                               GUARANTEE AGREEMENT

         This GUARANTEE AGREEMENT, dated as of        , 20   , is executed and
delivered by The Chubb Corporation., a New Jersey corporation (the "Guarantor"),
and Bank One Trust Company, N.A., a national banking association organized under
the laws of the United States, as trustee (the "Guarantee Trustee"), for the
benefit of the Holders (as defined herein) from time to time of the Preferred
Securities (as defined herein) of Chubb Capital Trust III, a Delaware statutory
trust (the "Issuer").

         WHEREAS, pursuant to an Amended and Restated Trust Agreement (the
"Trust Agreement"), dated as of       , 20     among the Trustees named therein,
the Guarantor, as Depositor, and the Holders from time to time of undivided
beneficial interests in the assets of the Issuer, the Issuer is issuing
of its         % Preferred Securities, Series A (liquidation preference $25 per
preferred security) (the "Preferred Securities") representing preferred
undivided beneficial interests in the assets of the Issuer and having the terms
set forth in the Trust Agreement;

         WHEREAS, the Preferred Securities will be issued by the Issuer and the
proceeds thereof, together with the proceeds from the issuance of the Issuer's
Common Securities (as defined below), will be used to purchase the Debentures
(as defined in the Trust Agreement) of the Guarantor which will be deposited
with Bank One Trust Company, N.A., as Property Trustee under the Trust
Agreement, as trust assets; and

         WHEREAS, as incentive for the Holders to purchase Preferred Securities
the Guarantor desires irrevocably and unconditionally to agree, to the extent
set forth herein, to pay to the Holders of the Preferred 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
Preferred Securities, which purchase the Guarantor hereby agrees shall benefit
the Guarantor, the Guarantor executes and delivers this Guarantee Agreement for
the benefit of the Holders from time to time of the Preferred Securities.

                                    ARTICLE I
                                   DEFINITIONS

         SECTION 1.1 Definitions.

         As used in this Guarantee Agreement, the terms set forth below shall,
unless the context otherwise requires, have the following meanings. Capitalized
or otherwise defined terms used but not otherwise defined herein shall have the
meanings assigned to such terms in the Trust Agreement as in effect on the date
hereof.

<PAGE>

         "Affiliate" of any specified Person means any other Person directly or
indirectly controlling or controlled by or under direct or indirect common
control with such specified Person, provided, however, that an Affiliate of the
Guarantor shall not be deemed to include the Issuer. For the purposes of this
definition, "control" when used with respect to any specified Person means the
power to direct the management and policies of such Person, directly or
indirectly, whether through the ownership of voting securities, by contract or
otherwise; and the terms "controlling" and "controlled" have meanings
correlative to the foregoing.

         "Common Securities" means the securities representing common beneficial
interests in the assets of the Issuer.

         "Debt" means, with respect to any Person, whether recourse is to all or
a portion of the assets of such Person and whether or not contingent, (i) every
obligation of such Person for money borrowed; (ii) every obligation of such
Person evidenced by bonds, debentures, notes or other similar instruments,
including obligations incurred in connection with the acquisition of property,
assets or businesses; (iii) every reimbursement obligation of such Person with
respect to letters of credit, bankers' acceptances or similar facilities issued
for the account of such Person; (iv) every obligation of such Person issued or
assumed as the deferred purchase price of property or services (but excluding
trade accounts payable or accrued liabilities arising in the ordinary course of
business); (v) every capital lease obligation of such Person; and (vi) every
obligation of the type referred to in clauses (i) through (v) of another Person
and all dividends of another Person the payment of which, in either case, such
Person has guaranteed or is responsible or liable, directly or indirectly, as
obligor or otherwise.

         "Event of Default" means a default by the Guarantor on any of its
payment or other obligations under this Guarantee Agreement; provided, however,
that, except with respect to a default in payment of any Guarantee Payments, the
Guarantor shall have received notice of default and shall not have cured such
default within 60 days after receipt of such notice.

         "Expenses" has the meaning specified in Section 3.3.

         "Guarantee Payments" means the following payments or distributions,
without duplication, with respect to the Preferred Securities, to the extent not
paid or made by or on behalf of the Issuer: (i) any accrued and unpaid
Distributions (as defined in the Trust Agreement) required to be paid on the
Preferred Securities, to the extent the Issuer shall have funds on hand
available therefor, (ii) the redemption price, including all accrued and unpaid
Distributions to the date of redemption (the "Redemption Price"), with respect
to the Preferred Securities called for redemption by the Issuer to the extent
the Issuer shall have funds on hand available therefor, and (iii) upon a
voluntary or involuntary termination, dissolution, winding-up or liquidation of
the Issuer, unless Debentures are

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distributed to the Holders, the lesser of (a) the aggregate of the liquidation
preference of $25 per Preferred Security plus accrued and unpaid Distributions
on the Preferred Securities to the date of payment to the extent the Issuer
shall have funds on hand available to make such payment and (b) the amount of
assets of the Issuer remaining available for distribution to Holders in
liquidation of the Issuer (in either case, the "Liquidation Distribution").

         "Guarantee Trustee" has the meaning specified in the preamble to this
Guarantee Agreement, until a Successor Guarantee Trustee has been appointed and
has accepted such appointment pursuant to the terms of this Guarantee Agreement
and thereafter means each such Successor Guarantee Trustee.

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

         "Indenture" means the Junior Subordinated Indenture dated as of April
     , 2003, as supplemented and amended between the Guarantor and Bank One
Trust Company, N.A., as trustee.

         "List of Holders" has the meaning specified in Section 2.2(a).

         "Majority in liquidation preference of the Securities" means, except as
provided by the Trust Indenture Act, a vote by the Holder(s), voting separately
as a class, of more than 50% of the liquidation preference of all then
outstanding Preferred Securities issued by the Issuer.

         "Officers' Certificate" means a certificate signed (i) by the chairman,
the vice chairman, the chief executive officer, the president or any vice
president, and (ii) by the treasurer or any assistant treasurer, or the
secretary or any assistant secretary of the Company, and delivered to the
Guarantee Trustee. Any Officers' Certificate delivered with respect to
compliance with a condition or covenant provided for in this Guarantee Agreement
shall include:

                  (a)      a statement that each officer signing the Officers'
         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 Officers' 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

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         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 Administration department of the Guarantee
Trustee with direct responsibility for the administration of this Guarantee
Agreement, including any vice-president, any assistant vice president, 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 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.

         "Senior Debt" means the principal of, premium, if any, and unpaid
interest on the following, whether outstanding at the date hereof or thereafter
incurred or created: (i) indebtedness of the Company for money borrowed
(including purchase-money obligations) evidenced by notes or other written
obligations, (ii) indebtedness of the Company evidenced by securities (other
than the securities issued under the Indenture and the Guarantee), debentures,
bonds or other securities issued under the provisions of an indenture or similar
instrument, (iii) obligations of the Company as lessee under capitalized leases
and leases of property made as part of any sale and leaseback transactions, (iv)
indebtedness of others of any of the kinds described in the preceding clauses
(i) through (iii) assumed or guaranteed by the Company and (v) renewals,
extensions and refundings of, and indebtedness and obligations of a successor
corporation issued in exchange for or in replacement of, indebtedness or
obligations of the kinds described in the preceding clauses (i) through (iv),
unless in the case of any particular indebtedness, obligation, renewal,
extension or refunding the instrument creating or evidencing the same or the
assumption or guarantee thereof expressly provides that such indebtedness,
obligation, renewal, extension or refunding is not superior in right of payment
to the Securities.

         "Successor Guarantee Trustee" means a successor Guarantee Trustee
possessing the qualifications to act as Guarantee Trustee under Section 4.1.

         "Trust Indenture Act" means the Trust Indenture Act of 1939, as
amended.

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                                   ARTICLE II
                               TRUST INDENTURE ACT

         SECTION 2.1 Trust Indenture Act; Application.

         (a)      This Guarantee Agreement is subject to the provisions of the
Trust Indenture Act that are required to be part of this Guarantee Agreement and
shall, to the extent applicable, be governed by such provisions.

         (b)      If and to the extent that any provision of this Guarantee
Agreement limits, qualifies or conflicts with the duties imposed by Sections 310
to 317, inclusive, of the Trust Indenture Act, such imposed duties shall
control.

         SECTION 2.2 List of Holders.

         (a)      The Guarantor shall furnish or cause to be furnished to the
Guarantee Trustee (a) semiannually, on or before February 15 and August 15 of
each year, a list, in such form as the Guarantee Trustee may reasonably require,
of the names and addresses of the Holders ("List of Holders") as of a date not
more than 15 days prior to the delivery thereof, and (b) at such other times as
the Guarantee Trustee may request in writing, within 30 days after the receipt
by the Guarantor of any such request, a List of Holders as of a date not more
than 15 days prior to the time such list is furnished, in each case to the
extent such information is in the possession or control of the Guarantor and is
not identical to a previously supplied list of Holders or has not otherwise been
received by the Guarantee Trustee in its capacity as such. The Guarantee Trustee
may destroy any List of Holders previously given to it on receipt of a new List
of Holders.

         (b)      The Guarantee Trustee shall comply with its obligations under
Section 311(a), Section 311(b) and Section 312(b) of the Trust Indenture Act.

         SECTION 2.3 Reports by the Guarantee Trustee.

         Within 60 days after May 15 of each year, the Guarantee Trustee shall
provide to the Holders such reports as are required by Section 313 of the Trust
Indenture Act, if any, in the form and in the manner provided by Section 313 of
the Trust Indenture Act. The Guarantee Trustee shall also comply with the
requirements of Section 313(d) of the Trust Indenture Act.

         SECTION 2.4 Periodic Reports to Guarantee Trustee.

         The Guarantor shall provide to the Guarantee Trustee, the Securities
and Exchange Commission and the Holders such documents, reports and information,
if any, as required by Section 314 of the Trust Indenture Act and the compliance
certificate

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required by Section 314 of the Trust Indenture Act in the form, in the manner
and at the times required by Section 314 of the Trust Indenture Act.

         SECTION 2.5 Evidence of Compliance with Conditions Precedent.

         The Guarantor shall provide to the Guarantee Trustee such evidence of
compliance with such conditions precedent, if any, provided for in this
Guarantee Agreement that relate to any of the matters set forth in Section
314(c) of the Trust Indenture Act. Any certificate or opinion required to be
given by an officer pursuant to Section 314(c)(1) may be given in the form of an
Officers' Certificate.

         SECTION 2.6 Events of Default; Waiver.

         The Holders of a Majority in liquidation preference of the Preferred
Securities may, by vote, on behalf of the Holders, waive any past Event of
Default and its consequences. Upon such waiver, any such Event of Default shall
cease to exist, and any Event of Default arising therefrom shall be deemed to
have been cured, for every purpose of this Guarantee Agreement, but no such
waiver shall extend to any subsequent or other default or Event of Default or
impair any right consequent therefrom.

         SECTION 2.7 Event 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, 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, that, except in the case of a
default in the payment of a Guarantee Payment, the Guarantee Trustee shall be
protected in withholding such notice if and so long as the Board of Directors,
the executive committee or a trust committee of directors and/or Responsible
Officers of the Guarantee Trustee in good faith determines that the withholding
of such notice is in the interests of the Holders.

         (b)      The Guarantee Trustee shall not be deemed to have knowledge of
any Event of Default unless a Responsible Officer of the Guarantee Trustee shall
have received written notice of such Event of Default.

         SECTION 2.8 Conflicting Interests.

         The Trust Agreement shall be deemed to be specifically described in
this Guarantee Agreement for the purposes of clause (i) of the first proviso
contained in Section 310(b) of the Trust Indenture Act.

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<PAGE>

                                  ARTICLE III
               POWERS, DUTIES AND RIGHTS OF THE GUARANTEE TRUSTEE

         SECTION 3.1 Powers and Duties of the Guarantee Trustee.

         (a)      This Guarantee Agreement shall be held by the Guarantee
Trustee for the benefit of the Holders, and the Guarantee Trustee shall not
transfer this Guarantee Agreement to any Person except a Holder exercising his
or her rights pursuant to Section 5.4(iv) 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, upon
acceptance by such Successor Guarantee Trustee of its appointment hereunder, 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 has occurred and is continuing, the
Guarantee Trustee shall, promptly upon receipt of written notice of such Event
of Default, enforce this Guarantee Agreement for the benefit of the Holders.

         (c)      The Guarantee Trustee, before the occurrence of any Event of
Default and after the curing of all Events of Default that may have occurred,
shall undertake to perform only such duties as are specifically set forth in
this Guarantee Agreement, and no implied duties or covenants shall be read into
this Guarantee Agreement against the Guarantee Trustee. In case an Event of
Default has occurred (that has not been cured or waived pursuant to Section
2.6), the Guarantee Trustee shall exercise such of the rights and powers vested
in it by this Guarantee Agreement, 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 Agreement 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 such 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 Agreement, and
                           the Guarantee Trustee shall not be liable except for
                           the performance of such duties and obligations as are
                           specifically set forth in this Guarantee Agreement;
                           and

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                                    (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 Agreement; but in
                           the case of any such certificates or opinions that by
                           any provision hereof or of the Trust Indenture Act
                           are specifically required to be furnished to the
                           Guarantee Trustee, the Guarantee Trustee shall be
                           under a duty to examine the same to determine whether
                           or not they conform on their face to the requirements
                           of this Guarantee Agreement;

                           (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 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 direction of the Holders
                  of not less than a Majority in liquidation preference of the
                  Preferred 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 Agreement; and

                           (iv)     no provision of this Guarantee Agreement
                  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 or liability is not reasonably assured to it under the
                  terms of this Guarantee Agreement or adequate indemnity
                  against such risk or liability is not reasonably assured to
                  it.

         SECTION 3.2 Certain Rights of Guarantee Trustee.

         (a)      Subject to the provisions of Section 3.1:

                  (i)      The Guarantee Trustee may rely and shall be fully
protected in acting or refraining from acting in good faith 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.

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                  (ii)     Any direction or act of the Guarantor contemplated by
this Guarantee Agreement shall be sufficiently evidenced by an Officers'
Certificate unless otherwise prescribed herein.

                  (iii)    Whenever, in the administration of this Guarantee
Agreement, the Guarantee Trustee shall deem it desirable that a matter be proved
or established before taking, suffering or omitting to take 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 rely upon
an Officers' Certificate which, upon receipt of such request from the Guarantee
Trustee, shall be promptly delivered by the Guarantor.

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

                  (v)      The Guarantee Trustee shall be under no obligation to
exercise any of the rights or powers vested in it by this Guarantee Agreement at
the request or direction of any Holder, unless such Holder shall have provided
to the Guarantee Trustee such adequate security and indemnity as would satisfy a
reasonable person in the position of the Guarantee Trustee, against the costs,
expenses (including attorneys' fees and expenses) 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 that,
nothing contained in this Section 3.2(a)(v) 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 Agreement.

                  (vi)     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.

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

                                       9

<PAGE>

                  (viii)   Whenever in the administration of this Guarantee
Agreement 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,
(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 acting in
accordance with such instructions.

         (b)      No provision of this Guarantee Agreement 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 to act in accordance with such power and
authority.

         SECTION 3.3 Indemnity.

         The Guarantor agrees to indemnify the Guarantee Trustee for, and to
hold it harmless against, any loss, liability or expense incurred without
negligence, bad faith or willful misconduct on the part of the Guarantee
Trustee, arising out of or in connection with the acceptance or administration
of this Guarantee Agreement, including the costs and expenses of defending
itself against any claim or liability in connection with the exercise or
performance of any of its powers or duties hereunder (collectively, "Expenses").
The Guarantee Trustee will not claim or exact any lien or charge on any
Guarantee Payments as a result of any amount due to it under this Guarantee
Agreement. To the fullest extent permitted by law, the Expenses (including
reasonable attorneys' fees and expenses) incurred by the Guarantee Trustee
referred to above shall be paid by the Guarantor in advance upon receipt of an
undertaking by or on behalf of the Guarantee Trustee to repay such amount if it
shall ultimately be determined that the Guarantee Trustee is not entitled to be
indemnified by the Guarantor as authorized in this Section 3.3. The obligations
of the Guarantor under this Section 3.3 shall survive termination of this
Guarantee Agreement and the removal or resignation of any Guarantee Trustee.

                                   ARTICLE IV
                                GUARANTEE TRUSTEE

         SECTION 4.1 Guarantee Trustee; Eligibility.

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

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

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                           (ii)     be a Person that is eligible pursuant to the
                  Trust Indenture Act to act as such and has a combined capital
                  and surplus of at least 50 million U.S. dollars ($50,000,000),
                  and shall be a corporation meeting the requirements of Section
                  310(a) of the Trust Indenture Act. If such corporation
                  publishes reports of condition at least annually, pursuant to
                  law or to the requirements of the supervising or examining
                  authority, then, for the purposes of this Section 4.1(a) and
                  to the extent permitted by the Trust Indenture Act, the
                  combined capital and surplus of such corporation 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 4.1(a), the Guarantee Trustee shall immediately
resign in the manner and with the effect set out in Section 4.2(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 and Guarantor shall in all respects comply with the provisions
of Section 310(b) of the Trust Indenture Act.

         SECTION 4.2 Appointment, Removal and Resignation of the Guarantee
         Trustee.

         (a)      Subject to Section 4.2(b), the Guarantee Trustee may be
appointed or removed without cause at any time by the Guarantor.

         (b)      The Guarantee Trustee shall not be removed 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 hereunder 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 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 4.2 within 60 days after
delivery to the Guarantor of an instrument of resignation, the resigning
Guarantee Trustee may petition any court of competent jurisdiction for
appointment of a Successor Guarantee Trustee. Such court

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<PAGE>

may thereupon, after prescribing such notice, if any, as it may deem proper,
appoint a Successor Guarantee Trustee.

                                    ARTICLE V
                                    GUARANTEE

         SECTION 5.1 Guarantee.

         The Guarantor irrevocably and unconditionally agrees to pay in full to
the Holders the Guarantee Payments (without duplication of amounts theretofore
paid by or on behalf of the Issuer), as and when due, regardless of any defense,
right of set-off or counterclaim which the Issuer may have or assert, other than
the defense of payment. 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.

         SECTION 5.2 Waiver of Notice and Demand.

         The Guarantor hereby waives notice of acceptance of the Guarantee
Agreement and of any liability to which it applies or may apply, presentment,
demand for payment, any right to require a proceeding first against the
Guarantee Trustee, 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 5.3 Obligations Not Affected.

         The obligations, covenants, agreements and duties of the Guarantor
under this Guarantee Agreement 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 Preferred 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 (other than an extension of
         time for payment of Distributions that results from the extension of
         any interest payment period on the Debentures as so provided in the
         Indenture), Redemption Price, Liquidation Distribution or any other
         sums payable under the terms of the Preferred Securities or the
         extension of time for the performance of any other obligation under,
         arising out of, or in connection with, the Preferred Securities;

                                       12

<PAGE>

                  (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 Preferred 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
         Preferred Securities;

                  (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 5.3 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 the
consent of, the Guarantor with respect to the happening of any of the foregoing.

         SECTION 5.4 Rights of Holders.

         The Guarantor expressly acknowledges that: (i) this Guarantee Agreement
will be deposited with the Guarantee Trustee to be held for the benefit of the
Holders; (ii) the Guarantee Trustee has the right to enforce this Guarantee
Agreement on behalf of the Holders; (iii) the Holders of a Majority in
liquidation preference of the Preferred 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 Agreement or to direct the
exercise of any trust or power conferred upon the Guarantee Trustee under this
Guarantee Agreement; and (iv) any Holder may institute a legal proceeding
directly against the Guarantor to enforce its rights under this Guarantee
Agreement, without first instituting a legal proceeding against the Guarantee
Trustee, the Issuer or any other Person.

         SECTION 5.5 Guarantee of Payment.

         This Guarantee Agreement creates a guarantee of payment and not of
collection. This Guarantee Agreement will not be discharged except by payment of
the Guarantee Payments in full (without duplication of amounts theretofore paid
by the Issuer) or upon distribution of Debentures to Holders as provided in the
Trust Agreement.

                                       13

<PAGE>

         SECTION 5.6 Subrogation.

         The Guarantor shall be subrogated to all (if any) rights of the Holders
against the Issuer in respect of any amounts paid to the Holders by the
Guarantor under this Guarantee Agreement and shall have the right to waive
payment by the Issuer pursuant to Section 5.1; provided, however, that the
Guarantor shall not (except to the extent required by mandatory provisions of
law) be entitled to enforce or exercise any rights which 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 Agreement, if, at the time of any
such payment, any amounts are due and unpaid under this Guarantee Agreement. If
any amount shall be paid to the Guarantor 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 5.7 Independent Obligations.

         The Guarantor acknowledges that its obligations hereunder are
independent of the obligations of the Issuer with respect to the Preferred
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
Agreement notwithstanding the occurrence of any event referred to in subsections
(a) through (g), inclusive, of Section 5.3 hereof.

                                   ARTICLE VI
                           COVENANTS AND SUBORDINATION

         SECTION 6.1 Subordination.

         This Guarantee Agreement will constitute an unsecured obligation of the
Guarantor and will rank subordinate and junior in right of payment to all Senior
Debt of the Guarantor.

         SECTION 6.2 Pari Passu Guarantees.

         This Guarantee shall rank pari passu with any similar Guarantees issued
by the Guarantor on behalf of the holders of Preferred Securities issued by
Chubb Capital Trust I and Chubb Capital Trust II, and other securities which are
similar to Preferred Securities that are guaranteed by the Guarantor pursuant to
an instrument that ranks pari passu with or junior in right of payment to this
Guarantee.

                                       14

<PAGE>

                                   ARTICLE VII
                                   TERMINATION

         SECTION 7.1 Termination.

         This Guarantee Agreement shall terminate and be of no further force and
effect upon (i) full payment of the Redemption Price of all Preferred
Securities, (ii) the distribution of Debentures to the Holders in exchange for
all of the Preferred Securities or (iii) full payment of the amounts payable in
accordance with the Trust Agreement upon liquidation of the Issuer.
Notwithstanding the foregoing, this Guarantee Agreement will continue to be
effective or will be reinstated, as the case may be, if at any time any Holder
must restore payment of any sums paid with respect to Preferred Securities or
this Guarantee Agreement.

                                  ARTICLE VIII
                                  MISCELLANEOUS

         SECTION 8.1 Successors and Assigns.

         All guarantees and agreements contained in this Guarantee Agreement
shall bind the successors, assigns, receivers, trustees and representatives of
the Guarantor and shall inure to the benefit of the Holders of the Preferred
Securities then outstanding. Except in connection with a consolidation, merger
or sale involving the Guarantor that is permitted under Article Eight of the
Indenture and pursuant to which the assignee agrees in writing to perform the
Guarantor's obligations hereunder, the Guarantor shall not assign its
obligations hereunder.

         SECTION 8.2 Amendments.

         Any amendment to this Guarantee Agreement shall be in writing and
executed by the Guarantor and Guarantee Trustee. Except with respect to any
changes which do not adversely affect the rights of the Holders in any material
respect (in which case no consent of the Holders will be required), this
Guarantee Agreement may only be amended with the prior approval of the Holders
of not less than a Majority in liquidation preference of all the outstanding
Preferred Securities. The provisions of Article VI of the Trust Agreement
concerning meetings of the Holders shall apply to the giving of such approval.
The Guarantee Trustee shall not be required to enter into any amendment to this
Guarantee Agreement which affects its own rights, duties or immunities under
this Guarantee Agreement. The Guarantee Trustee shall be entitled to receive and
conclusively rely on an Opinion of Counsel and an Officer's Certificate stating
that any amendment to this Guarantee Agreement is in compliance with this
Guarantee Agreement.

                                       15

<PAGE>

         SECTION 8.3 Notices.

         Any notice, request or other communication required or permitted to be
given hereunder shall be in writing, duly signed by the party giving such
notice, and delivered, telecopied or mailed by first class mail as follows:

                  (a)      if given to the Guarantor, to the address set forth
         below or such other address as the Guarantor may give notice of to the
         Holders:

                           The Chubb Corporation
                           15 Mountain View Road
                           P.O. Box 1615
                           Warren, New Jersey 07061
                           Facsimile No.: (908) 903-2003
                           Attention: Secretary

                  (b)      if given to the Issuer, in care of the Guarantee
         Trustee, at the Issuer's (and the Guarantee Trustee's) address set
         forth below or such other address as the Guarantee Trustee on behalf of
         the Issuer may give notice to the Holders:

                           Chubb Capital Trust III
                           c/o The Chubb Corporation
                           15 Mountain View Road
                           P.O. Box 1615
                           Warren, New Jersey 07061
                           Facsimile No.: (908) 903-2003
                           Attention: Secretary

                           with a copy to:

                           Bank One Trust Company, N.A.
                           153 West 51st Street
                           New York, New York 10019
                           Facsimile No.: (212) 373-1383

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

         All notices hereunder 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

                                       16

<PAGE>

document shall be deemed to have been delivered on the date of such refusal or
inability to deliver.

         SECTION 8.4 Benefit.

         This Guarantee Agreement is solely for the benefit of the Holders and
is not separately transferable from the Preferred Securities.

         SECTION 8.5 Interpretation.

         In this Guarantee Agreement, unless the context otherwise requires:

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

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

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

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

              (e)      a term defined in the Trust Indenture Act has the same
         meaning when used in this Guarantee Agreement unless otherwise defined
         in this Guarantee Agreement or unless the context otherwise requires;

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

              (g)      the masculine, feminine or neuter genders used herein
         shall include the masculine, feminine and neuter genders.

         SECTION 8.6 GOVERNING LAW.

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

                                       17

<PAGE>

         SECTION 8.7 Counterparts

         This instrument may be executed in any number of counterparts, each of
which so executed shall be deemed to be an original, but all such counterparts
shall together constitute but one and the same instrument.

                                       18

<PAGE>

         IN WITNESS WHEREOF, the parties hereto have caused this Guarantee
Agreement to be duly executed as of the day and year first above written.

                                                THE CHUBB CORPORATION

                                                By:_____________________________
                                                Name:
                                                Title:

                                                BANK ONE TRUST COMPANY, N.A., as
                                                Guarantee Trustee

                                                By:_____________________________
                                                Name:
                                                Title:

<PAGE>

                             CROSS-REFERENCE TABLE*

<TABLE>
<CAPTION>
    Section of                                                                 Section of
Trust Indenture Act                                                             Guarantee
of 1939, as amended                                                             Agreement
-------------------                                                             ---------
<S>                                                                            <C>
310(a).................................................................        4.1(a)
310(b).................................................................        4.1(c), 2.8
310(c).................................................................        Inapplicable
311(a).................................................................        2.2(b)
311(b).................................................................        2.2(b)
311(c).................................................................        Inapplicable
312(a).................................................................        2.2(a)
312(b).................................................................        2.2(b)
313....................................................................        2.3
314(a).................................................................        2.4
314(b).................................................................        Inapplicable
314(c).................................................................        2.5
314(d).................................................................        Inapplicable
314(e).................................................................        1.1, 2.5, 3.2
314(f).................................................................        2.1, 3.2
315(a).................................................................        3.1(d)
315(b).................................................................        2.7
315(c).................................................................        3.1
315(d).................................................................        3.1(d)
316(a).................................................................        1.1, 2.6, 5.4
316(b).................................................................        5.3
316(c).................................................................        8.2
317(a).................................................................        Inapplicable
317(b).................................................................        Inapplicable
318(a).................................................................        2.1(b)
318(b).................................................................        2.1
318(c).................................................................        2.1(a)
</TABLE>

----------
*   This Cross-Reference Table does not constitute part of the Guarantee
    Agreement and shall not affect the interpretation of any of its terms or
    provisions.

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