EXHIBIT 5



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                      COMMON SECURITIES GUARANTEE AGREEMENT

                         Allmerica Financial Corporation

                          Dated as of February 3, 1997





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                                TABLE OF CONTENTS
                                -----------------
                                                                            Page
                                                                            ----

ARTICLE I  DEFINITIONS AND INTERPRETATION..................................... 3

ARTICLE II  GUARANTEE......................................................... 4

     SECTION 2.1.  Guarantee.................................................. 4
     SECTION 2.2.  Waiver of Notice and Demand................................ 4
     SECTION 2.3.  Obligations Not Affected................................... 4
     SECTION 2.4.  Rights of Holders.......................................... 5
     SECTION 2.5.  Guarantee of Payment....................................... 5
     SECTION 2.6.  Subrogation................................................ 5
     SECTION 2.7.  Independent Obligations.................................... 6

ARTICLE III  LIMITATION OF TRANSACTIONS; SUBORDINATION........................ 6

     SECTION 3.1.  Limitation of Transactions................................. 6
     SECTION 3.2.  Ranking.................................................... 7

ARTICLE IV  TERMINATION....................................................... 7

     SECTION 4.1.  Termination................................................ 7

ARTICLE V  MISCELLANEOUS...................................................... 8

     SECTION 5.1.  Successors and Assigns..................................... 8
     SECTION 5.2.  Amendments................................................. 8
     SECTION 5.3.  Notices.................................................... 8
     SECTION 5.4.  Benefit.................................................... 9
     SECTION 5.5.  Governing Law.............................................. 9


                                      -i-

 
                      COMMON SECURITIES GUARANTEE AGREEMENT

         This GUARANTEE AGREEMENT (the "Common Securities Guarantee"), dated as
of February 3, 1997, is executed and delivered by Allmerica Financial
Corporation, a Delaware corporation (the "Guarantor"), for the benefit of the
Holders (as defined herein) from time to time of the Common Securities (as
defined herein) of AFC Capital Trust I, a Delaware business trust (the
"Issuer").

         WHEREAS, pursuant to an Amended and Restated Declaration of Trust (the
"Declaration"), dated as of February 3, 1997, among the Trustees of the Issuer
named therein, the Guarantor, 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 9,279 common securities designated the 8.207% Common
Securities (the "Common Securities"), having an aggregate stated liquidation
amount of $9,279,000;

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

         WHEREAS, the Guarantor is also executing and delivering a guarantee
agreement (the "Series A Capital Securities Guarantee") for the benefit of the
holders of the Series A Capital Securities (as defined in the Declaration) and
upon consummation of the Exchange Offer (as defined in the Declaration) will
execute and deliver a guarantee agreement (the "Series B Capital Securities
Guarantee") for the benefit of the holders of the Series B Capital Securities
(as defined in the Declaration), each in substantially identical terms to this
Common Securities Guarantee, except that if an Event of Default (as defined in
the Declaration) has occurred and is continuing, the rights of Holders of the
Common Securities to receive Guarantee Payments under this Common Securities
Guarantee are subordinated to the rights of holders of Capital Securities to
receive Guarantee Payments under the Series A Capital Securities Guarantee and
the Series B Capital Securities Guarantee, as the case may be.

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

                                      -2-

 
                                   ARTICLE I
                        DEFINITIONS AND INTERPRETATION

         In this Common Securities Guarantee, unless the context otherwise
requires:

SECTION 1.1. Capitalized terms used in this Common Securities Guarantee but not
defined in the preamble above have the respective meanings assigned to them in
this Article I;

SECTION 1.2. Terms defined in the Declaration as at the date of execution of
this Common Securities Guarantee have the same meaning when used in this Common
Securities Guarantee unless otherwise defined in this Common Securities
Guarantee;

SECTION 1.3.  a term defined anywhere in this Common Securities Guarantee has 
the same meaning throughout;

SECTION 1.4. all references to "the Common Securities Guarantee" or "this Common
Securities Guarantee" are to this Common Securities Guarantee as modified,
supplemented or amended from time to time;

SECTION 1.5. all references in this Common Securities Guarantee to Articles and
Sections are to Articles and Sections of this Common Securities Guarantee unless
otherwise specified; and

SECTION 1.6.  a reference to the singular includes the plural and vice versa.

         "Guarantee Payments" means the following payments or distributions,
without duplication, with respect to the Common Securities, to the extent not
paid or made by the Issuer: (i) any accrued and unpaid Distributions that are
required to be paid on such Common Securities to the extent the Issuer has funds
on hand legally available therefor at such time, (ii) the redemption price,
including all accrued and unpaid Distributions to the date of redemption (the
"Redemption Price") to the extent the Issuer has funds on hand legally available
therefor at such time, with respect to any Common Securities called for
redemption by the Issuer, and (iii) upon a voluntary or involuntary termination
and liquidation of the Issuer (other than in connection with the distribution of
Debentures to the Holders in exchange for Common Securities as provided in the
Declaration), the lesser of (a) the aggregate of the liquidation amount and all
accumulated and unpaid Distributions on the Common Securities to the date of
payment, to the extent the Issuer has funds on hand legally available therefor,
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"). If an Event of Default has occurred and is continuing, no
Guarantee Payments with respect to the Common Securities shall be made until
holders of Capital Securities shall be paid in full the Guarantee Payments to
which they are entitled under the Series A Capital Securities Guarantee and the
Series B Capital Securities Guarantee.

                                      -3-

 
         "Holder" means any holder, as registered on the books and records of 
the Issuer, of any Common Securities.

         "Issuer" means AFC Capital Trust I.

         "Other Guarantees" means all guarantees to be issued by the Guarantor
with respect to common securities (if any) similar to the Common Securities
issued by other trusts to be established by the Guarantor (if any), in each case
similar to the Issuer.

                                  ARTICLE II
                                   GUARANTEE

SECTION 2.1.  Guarantee
              ---------

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

SECTION 2.2.  Waiver of Notice and Demand.
              ---------------------------

     The Guarantor hereby waives notice of acceptance of this Common Securities
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 2.3.  Obligations Not Affected.
              ------------------------

     Except as otherwise provided herein, the obligations, covenants, agreements
and duties of the Guarantor under this Common Securities 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 Common 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, Liquidation Distribution or any
other sums payable under the terms of the Common Securities or the extension of
time for the performance of any other obligation under, arising out of, or in
connection with, the Common Securities (other than an 

                                      -4-

 
extension of time for payment of Distributions, Redemption Price, Liquidation
Distribution or other sum payable that results from the extension of any
interest payment period on 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 Common 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 Common 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 2.3 that the obligations of the Guarantor with respect to the
Guarantee Payments 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 2.4.  Rights of Holders
              -----------------

     The Guarantor expressly acknowledges that any Holder may institute a legal
proceeding directly against the Guarantor to enforce its rights under this
Common Securities Guarantee, without first instituting a legal proceeding
against the Issuer or any other Person.

SECTION 2.5.  Guarantee of Payment
              --------------------

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

SECTION 2.6.  Subrogation
              -----------   

     The Guarantor shall be subrogated to all (if any) rights of the Holders
against the Issuer in respect of any amounts paid to such Holders by the
Guarantor under this Common Securities Guarantee; provided, however, that the
                                                  --------  ------- 
Guarantor shall not (except to the extent required 


                                      -5-

 
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 Common
Securities Guarantee, if, at the time of any such payment, any amounts are due
and unpaid under this Common Securities Guarantee. 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 2.7.  Independent Obligations
              -----------------------

     The Guarantor acknowledges that its obligations hereunder are independent
of the obligations of the Issuer with respect to the Common Securities and that
the Guarantor shall be liable as principal and as debtor hereunder to make
Guarantee Payments pursuant to the terms of this Common Securities Guarantee
notwithstanding the occurrence of any event referred to in subsections (a)
through (g), inclusive, of Section 2.3 hereof.

                                   ARTICLE III
                    LIMITATION OF TRANSACTIONS; SUBORDINATION

SECTION 3.1.  Limitation of Transactions
              --------------------------

     So long as any Common Securities remain outstanding, the Guarantor shall
not (i) 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 (which includes common and preferred stock), (ii) make any payment
of principal, interest or premium, if any, on or repay, repurchase or redeem any
debt securities of the Guarantor (including any Other Debentures) that rank pari
passu with or junior in right of payment to the Junior Subordinated Debentures
or (iii) make any guarantee payments with respect to any guarantee by the
Guarantor of any securities of any subsidiary of the Guarantor (including Other
Guarantees) if such guarantee ranks pari passu with or junior in right of
payment to the Junior Subordinated Debentures (other than (a) dividends or
distributions in shares of or options, warrants or rights to subscribe for or
purchase shares of, common stock of the Guarantor, (b) any declaration of a
dividend in connection with the implementation of a stockholder's rights plan,
or the issuance of stock under any such plan in the future, or the redemption or
repurchase of any such rights pursuant thereto, (c) payments under the
Guarantee, (d) as a direct result of, and only to the extent required in order
to avoid the issuance of fractional shares of capital stock following, a
reclassification of the Guarantor's capital stock or the exchange or conversion
of one class or series of the Guarantor's capital stock for another class or
series of the Guarantor's capital stock or pursuant to an acquisition in which
fractional shares of the Guarantor's capital stock would otherwise be issued,
(e) 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, and (f) purchases of common 


                                      -6-

 
stock related to the issuance of common stock or rights under any benefit plan
for directors, officers, agents or employees of the Guarantor or its
subsidiaries or any of the Guarantor's dividend reinvestment or director,
officer, agent or employee stock purchase plans) if at such time (i) an Event of
Default (as defined in the Indenture) shall have occurred and be continuing, or
would occur upon the taking of any action specified in clauses (i) through (iii)
above, (ii) there shall have occurred any event of which the Guarantor has
actual knowledge that (a) is, or with the giving of notice or the lapse of time,
or both, would be an Event of Default (as defined in the Indenture) and (b) in
respect of which the Guarantor shall not have taken reason able steps to cure,
(iii) if such Debentures are held by the Property Trustee, the Guarantor shall
be in default with respect to its payment of any obligations under this Series A
Capital Securities Guarantee or (iv) the Guarantor shall have given notice of
its election of the exercise of its right to extend the interest payment period
pursuant to Section 16.01 of the Indenture or with respect to certain other
debentures of the Guarantor and any such extension shall be continuing.

SECTION 3.2.  Ranking
              -------

     This Common Securities Guarantee will constitute an unsecured obligation of
the Guarantor and will rank (i) subordinate and junior in right of payment to
Senior Indebtedness (as defined in the Indenture), to the same extent and in the
same manner that the Debentures are subordinated to Senior Indebtedness pursuant
to the Indenture, it being understood that the terms of Article XV of the
Indenture shall apply to the obligations of the Guarantor under this Common
Securities Guarantee as if (x) such Article XV were set forth herein in full and
(y) such obligations were substituted for the term "Securities" appearing in
such Article XV, (ii) pari passu with the Debentures and with the most senior
preferred or preference stock now or hereafter issued by the Guarantor and with
any Other Guarantee and any guarantee now or hereafter entered into by the
Guarantor in respect of any preferred or preference stock of any Affiliate of
the Guarantor, and (iii) senior to the Guarantor's common stock.

                                   ARTICLE IV
                                  TERMINATION

SECTION 4.1.  Termination
              ----------- 

     This Common Securities Guarantee shall terminate (i) upon full payment of
the Redemption Price of all Common Securities, (ii) upon the distribution of the
Debentures to all the Holders or (iii) upon full payment of the amounts payable
in accordance with the Declaration upon liquidation of the Issuer.
Notwithstanding the foregoing, this Common Securities Guarantee 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 under the Common Securities or
under this Common Securities Guarantee.


                                      -7-

 
                                    ARTICLE V
                                  MISCELLANEOUS

SECTION 5.1.  Successors and Assigns
              ----------------------

     All guarantees and agreements contained in this Common Securities Guarantee
shall bind the successors, assigns, receivers, trustees and representatives of
the Guarantor and shall inure to the benefit of the Holders then outstanding.

SECTION 5.2.  Amendments
              ----------

     Except with respect to any changes which do not adversely affect the
rights of Holders (in which case no consent of Holders will be required), this
Common Securities Guarantee may only be amended with the prior approval of the
Holders of at least a majority in liquidation amount of all the outstanding
Common Securities. The provisions of Section 12.2 of the Declaration with
respect to meetings of Holders apply to the giving of such approval.

SECTION 5.3.  Notices
              -------

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

     (a)   if given to the Issuer, in care of the Administrative Trustee at
the Issuer's mailing address set forth below (or such other address as the
Issuer may give notice of to the Holders):

           AFC Capital Trust I
           c/o Allmerica Financial Corporation
           440 Lincoln Street
           Worcester, Massachusetts  01653
           Attention:  Chief Financial Officer
           Telecopy:         (508) 852-7588

     (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):

           Allmerica Financial Corporation
           440 Lincoln Street
           Worcester, Massachusetts  01653
           Attention:  Chief Financial Officer
           Telecopy:         (508) 852-7588


                                      -8-

 
     (c)   if given to any Holder, 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 5.4.  Benefit
              -------

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

SECTION 5.5.  Governing Law
              -------------

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

                                      -9-

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

                                  ALLMERICA FINANCIAL CORPORATION



                                  By:/s/ Edward J. Parry III
                                     -----------------------------
                                      Name:  Edward J. Parry III
                                      Title: Vice President and Chief
                                             Financial Officer

                                     -10-