EXHIBIT 10.1

CABOT CORPORATION
1999 EQUITY INCENTIVE PLAN

Amendment

     Pursuant to the terms of the Cabot Corporation 1999 Equity Incentive Plan
(the “Plan”), Cabot Corporation, as authorized by its Board of Directors on
January 14, 2005, hereby amends the Plan to add a new Section 8.10 to the Plan,
which reads as follows:

“Section 8.10. Operation of Plan in accordance with Section 409A of the Internal
Revenue Code.

The Plan will be operated in a manner consistent with a good-faith, reasonable
interpretation of Section 409A of the Code and applicable guidance thereunder,
as determined by the Committee in its discretion. Each Award subject to
Section 409A of the Code will be structured accordingly, and any action taken
with respect to any such Award will be construed and administered consistent
with the intent that such Award comply with the requirements of Section 409A.”

     IN WITNESS WHEREOF, Cabot Corporation has caused this instrument of
amendment to be executed as of January 14, 2005 by a duly authorized officer.

     

  CABOT CORPORATION
 
   

  By: /s/ Robby D. Sisco

  Name: Robby D. Sisco
Title: Vice President