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                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

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

                                    FORM 8-A

                FOR REGISTRATION OF CERTAIN CLASSES OF SECURITIES
                     PURSUANT TO SECTION 12(b) OR (g) OF THE
                         SECURITIES EXCHANGE ACT OF 1934

                               TRENWICK GROUP INC
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             (Exact Name of Registrant as Specified in Its Charter)


          Delaware                                              06-1152790
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(State of Incorporation or Organization)                       (IRS Employer
                                                             Identification No.)

Metro Center, One Station Place, Stamford, Connecticut             06902
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    (Address of Principal Executive Offices)                     (Zip Code)

     If this form relates to the registration of a class of securities pursuant
to Section 12(b) of the Exchange Act and is effective pursuant to General
Instruction A.(c), check the following box.                                  / /

     If this form relates to the registration of a class of securities pursuant
to Section 12(g) of the Exchange Act and is effective pursuant to General
Instruction A.(d), check the following box.                                 /X/

     Securities Act registration statement to which this form relates (if
applicable).

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

          Title of each class                   Name of each exchange
          to be so registered                   on which each class is
                                                   to be registered
                 None

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

                         Preferred Stock Purchase Rights

                                (Title of Class)
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ITEM 1.   DESCRIPTION OF SECURITIES TO BE REGISTERED.

      The Board of Directors of Trenwick Group Inc. (the "Company") has 
declared a dividend distribution of one Right for each outstanding
share of Common Stock to shareholders of record at the close of business on
September 24, 1997 (the "Record Date"). Each Right entitles the registered
holder to purchase from the Company one two-hundredths of a share of Series B
Junior Participating Preferred Stock, par value $.10 per share (the "Preferred
Stock"), at a Purchase Price of $125, subject to adjustment. The description
and terms of the Rights are set forth in a Rights Agreement (the "Rights
Agreement") between the Company and First Chicago Trust Company of New York,
as Rights Agent.

      Initially, the Rights will be attached to all Common Stock certificates
representing shares then outstanding, and no separate Rights Certificates will
be distributed. The Rights will separate from the Common Stock and a
Distribution Date will occur upon the earlier of (i) ten (10) days following a
public announcement that a person or group of affiliated or associated persons
(an "Acquiring Person") has acquired, or obtained the right to acquire,
beneficial ownership of fifteen percent (15%) or more of the outstanding shares
of Common Stock (the "Stock Acquisition Date"), other than as a result of
repurchases of stock by the Company or certain inadvertent actions by
institutional or certain other shareholders, or (ii) the commencement of a
tender offer or exchange offer that would result in a person or group
beneficially owning fifteen percent (15%) or more of such outstanding shares of
Common Stock. Until the Distribution Date, (i) the Rights will be evidenced by
the Common Stock certificates and will be transferred with and only with such
Common Stock certificates, (ii) new Common Stock certificates issued after the
Record Date will contain a notation incorporating the Rights Agreement by
reference and (iii) the surrender for transfer of any certificates for Common
Stock outstanding will also constitute the transfer of the Rights associated
with the Common Stock represented by such certificate. Pursuant to the Rights
Agreement, the Company reserves the right to require prior to the occurrence of
a Triggering Event (as defined below) that, upon any exercise of Rights, a
number of Rights be exercised so that only whole shares of Preferred Stock will
be issued.

      The Rights are not exercisable until the Distribution Date and will expire
at the close of business on September 23, 2007, unless earlier redeemed or
exchanged by the Company as described below.

      As soon as practicable after the Distribution Date, Rights Certificates
will be mailed to holders of record of the Common Stock as of the close of
business on the Distribution Date and, thereafter, the separate Rights
Certificates alone will represent the Rights. Except as otherwise determined by
the Board, only shares of Common Stock issued prior to the Distribution Date
will be issued with Rights.


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      In the event that a Person becomes an Acquiring Person (except pursuant to
an offer for all outstanding shares of Common Stock that the independent
directors determine (i) not to be inadequate and (ii) to otherwise be in the
best interests of the Company and its shareholders), each holder of a Right will
thereafter have the right to receive, upon exercise, Common Stock (or, in
certain circumstances, cash, property or other securities of the Company) having
a value equal to two times the exercise price of the Right. Notwithstanding any
of the foregoing, following the occurrence of the event set forth in this
paragraph, all Rights that are, or (under certain circumstances specified in the
Rights Agreement) were, beneficially owned by any Acquiring Person will be null
and void.

      For example, at an exercise price of $125 per Right, each Right not owned
by an Acquiring Person (or by certain related parties) following an event set
forth in the preceding paragraph would entitle its holder to purchase $250 worth
of Common Stock (or other consideration, as noted above) for $125. Assuming that
the Common Stock had a per share value of $36.50 at such time, the holder of 
each valid Right would be entitled to purchase approximately 6.8 shares of 
Common Stock for $125.

      In the event that, at any time following the Stock Acquisition Date, (i)
the Company is acquired in a merger or other business combination transaction
(other than a merger which follows an offer described in the second preceding
paragraph), or (ii) fifty percent (50%) or more of the Company's assets or
earning power is sold or transferred, each holder of a Right (except Rights
which previously have been voided as set forth above) shall thereafter have the
right to receive, upon exercise, common stock of the acquiring company having a
value equal to two times the exercise price of the Right. The events set forth
in this paragraph and in the second preceding paragraph are referred to as the
"Triggering Events."

      At any time until the Stock Acquisition Date, the Company may redeem the
Rights in whole, but not in part, at a price of $.01 per Right (payable in cash,
Common Stock or other consideration deemed appropriate by the Board).
Immediately upon the action of the Board ordering redemption of the Rights, the
Rights will terminate and the only right of the holders of Rights will be to
receive the $.01 redemption price. The foregoing notwithstanding, the Rights
generally may not be redeemed for one hundred eighty (180) days following a
change in a majority of the Board as a result of a proxy contest.

      At any time after the acquisition by a person or group of affiliated or
associated persons of beneficial ownership of 15% or more of the outstanding
shares and prior to the acquisition by such person or group of 50% or more of
the outstanding shares of Common Stock, the Board of Directors may exchange the
Rights (other than Rights owned by such person or group which have become void),
in whole or in part, at an exchange ratio of one share of Common Stock, or one
two-hundredths of a share of Preferred Stock (or of a share of a class or series
of the Company's preferred stock


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having equivalent rights, preferences and privileges), per Right (subject to
adjustment).

      Until a Right is exercised, the holder thereof, as such, will have no
rights as a shareholder of the Company, including, without limitation, the right
to vote or to receive dividends. While the distribution of the Rights will not
be taxable to shareholders or to the Company, shareholders may, depending upon
the circumstances, recognize taxable income in the event that the Rights become
exercisable for Common Stock (or other consideration) of the Company or for
common stock of the acquiring company as set forth above.

      Any of the provisions of the Rights Agreement may be amended by the Board
prior to the Distribution Date. After the Distribution Date, the provisions of
the Rights Agreement may be amended by the Board in order to cure any ambiguity,
to make changes which do not adversely affect the interests of holders of
Rights, or to shorten or lengthen any time period under the Rights Agreement;
provided, however, that no amendment may be made at such time as the Rights are
not redeemable.

      As of September 19, 1997, there were 11,951,060 shares of Common Stock of
the Company outstanding. As of September 19, 1997, options to purchase 911,195
shares of Common Stock were outstanding. Each share of Common Stock of the
Company outstanding at the close of business on September 24, 1997 will receive
one Right. So long as the Rights are attached to the Common Stock, one
additional Right (as such number may be adjusted pursuant to the provisions of
the Rights Agreement) shall be deemed to be delivered for each share of Common
Stock issued or transferred by the Company in the future. In addition, following
the Distribution Date and prior to the expiration or redemption of the Rights,
the Company may issue Rights when it issues Common Stock only if the Board deems
it to be necessary or appropriate, or in connection with the issuance of shares
of Common Stock pursuant to the exercise of stock options or under employee
plans or upon the exercise, conversion or exchange of certain securities of the
Company. Two hundred thousand shares of Preferred Stock are initially reserved
for issuance upon exercise of the Rights.

      The Rights may have certain anti-takeover effects. The Rights will cause
substantial dilution to a person or group that attempts to acquire the Company
in a manner which causes the Rights to become discount Rights unless the offer
is conditional on a substantial number of Rights being acquired. The Rights,
however, should not affect any prospective offeror willing to make an offer at a
fair price and otherwise in the best interests of the Company and its
shareholders as determined by a majority of the Directors who are not affiliated
with the person making the offer, or willing to negotiate with the Board. The
Rights should not interfere with any merger or other business combination
approved by the Board since the Board may, at its option, at any time until the
Stock Acquisition Date redeem all but not less than all the then outstanding
Rights at the Redemption Price.


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      The Rights Agreement, dated as of September 24, 1997, between the Company
and First Chicago Trust Company of New York, as Rights Agent, specifying the
terms of the Rights and including the form of Certificate of Designation,
Preferences and Rights setting forth the terms of the Preferred Stock as an
exhibit thereto, is attached hereto as an exhibit. The foregoing description of
the Rights Agreement does not purport to be complete and is qualified by
reference to the Rights Agreement attached hereto as an exhibit, which is
incorporated herein by reference.

ITEM 2.   EXHIBITS.

      1     Rights Agreement, dated as of September 24, 1997, between Trenwick
            Group Inc. and First Chicago Trust of New York, as Rights Agent,
            including the form of Certificate of Designation, Preferences and
            Rights setting forth the terms of the Series B Junior Participating
            Preferred Stock, par value $.10 per share, as Exhibit A, the form of
            Rights Certificate as Exhibit B and the Summary of Rights to
            Purchase Preferred Stock as Exhibit C. Pursuant to the Rights
            Agreement, printed Rights Certificates will not be mailed until
            after the Distribution Date (as such term is defined in the Rights
            Agreement).


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                                    SIGNATURE

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

                                          Trenwick Group Inc.

                                          By:/s/ James F. Billett, Jr.
                                             -----------------------------------
                                             Name:  James F. Billett, Jr.
                                             Title:   Chairman of the Board,
                                                      President and Chief
                                                      Executive Officer

Dated: September 24, 1997


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