Exhibit 4.1

                       AMENDMENT NO. 1 TO RIGHTS AGREEMENT

1.    GENERAL BACKGROUND. In accordance with Section 28 of the Rights Agreement
      between The First National Bank of Boston, as Rights Agent (now known as
      "Fleet National Bank" (the "Rights Agent") and Cabot Corporation (the
      "Corporation") dated November 10, 1995 (the "Agreement"), the Rights Agent
      and the Corporation desire to amend Section 21 of the Agreement as set
      forth below.

2.    EFFECTIVENESS. This Amendment shall be effective as of July 12, 2002 (the
      "Amendment") and all defined terms and definitions in the Agreement shall
      be the same in the Amendment except as specifically revised by the
      Amendment.

3.    AMENDMENT TO SECTION 21. Section 21 in the Agreement entitled "Change of
      Rights Agent" is hereby deleted in its entirety and replaced with the
      following Section 21:

            "Change of Rights Agent. The Rights Agent or any successor Rights
            Agent may resign and be discharged from its duties under this
            Agreement upon 30 days' notice in writing mailed to the Corporation
            and to each transfer agent of the Common Shares or Preferred Shares
            by registered or certified mail and to the holders of the Right
            Certificates by first-class mail. The Corporation may remove the
            Rights Agent or any successor Rights Agent upon 60 days' notice in
            writing, mailed to the Rights Agent or any successor Rights Agent,
            as the case may be, and to each transfer agent of the Common Shares
            or Preferred Shares by registered or certified mail, and to the
            holders of the Right Certificates by first-class mail. If the Rights
            Agent shall resign or be removed or shall otherwise become incapable
            of acting, the Corporation shall appoint a successor to the Rights
            Agent. If the Corporation shall fail to make such appointment within
            a period of 60 days after giving notice of such removal or after it
            has been notified in writing of such resignation or incapacity by
            the resigning or incapacitated Rights Agent or by the holder of a
            Right Certificate (who shall, with such notice, submit such holder's
            Right Certificate for inspection by the Corporation), then the
            registered holder of any Right Certificate may apply to any court of
            competent jurisdiction for the appointment of a new Rights Agent.
            Any successor Rights Agent, whether appointed by the Corporation or
            by such a court, shall be a corporation or trust company organized
            and doing business under the laws of the United States, or of the
            State of New York or the Commonwealth of Massachusetts (or of any
            other state of the United States so long as such corporation is
            authorized to do business as a banking institution in the State of
            New York, or the Commonwealth of Massachusetts), in good standing,
            having a principal office in the State of New York or the
            Commonwealth of Massachusetts which is authorized under such laws to
            exercise corporate trust or stock transfer powers and is subject to
            supervision or examination by federal or state authority and which
            has individually or combined with an affiliate at the time of its
            appointment as Rights Agent a combined capital and surplus of at
            least $100 million dollars. After appointment, the successor Rights
            Agent shall be vested with the same powers,

            rights, duties and responsibilities as if it had been originally
            named as Rights Agent without further act or deed; but the
            predecessor Rights Agent shall deliver and transfer to the successor
            Rights Agent any property at the time held by it hereunder, and
            execute and deliver any further assurance, conveyance, act or deed
            necessary for the purpose. Not later than the effective date of any
            such appointment the Corporation shall file notice thereof in
            writing with the predecessor Rights Agent and each transfer agent of
            the Common Shares or Preferred Shares, and mail a notice thereof in
            writing to the registered holders of the Right Certificates. Failure
            to give any notice provided for in this Section 21, however, or any
            defect therein, shall not affect the legality or validity of the
            resignation or removal of the Rights Agent or the appointment of the
            successor Rights Agent, as the case may be."

4.    Except as amended hereby, the Agreement and all schedules or exhibits
      thereto shall remain in full force and effect.

IN WITNESS WHEREOF, the parties hereto have caused this Amendment to be executed
in their names and on their behalf by and through their duly authorized
officers, as of this 12th day of July, 2002.


                                   
CABOT CORPORATION                     THE FIRST NATIONAL BANK
                                      OF BOSTON (NOW KNOWN AS
                                      FLEET NATIONAL BANK)

/s/ Hoil Kim                          /s/ Katherine S. Anderson
- ------------------------------        --------------------------------
By: Hoil Kim                          By:  Katherine S. Anderson
Title: Vice President and             Title:  Managing Director
        General Counsel