UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

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

                                    FORM 8-K


                                 CURRENT REPORT
     Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934


                Date of Report (date of earliest event reported):
                                January 17, 2005


                       Cabot Microelectronics Corporation
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             (Exact name of registrant as specified in its charter)


              Delaware                      000-30205            36-4324765
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  (State or other jurisdiction of          (Commission          (IRS Employer
           incorporation)                  File Number)        Identification)


             870 Commons Drive, Aurora, Illinois             60504
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          (Address of principal executive offices)        (Zip Code)

                                 (630) 375-6631
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              (Registrant's telephone number, including area code)

                                 Not applicable
        ----------------------------------------------------------------
          (Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to
simultaneously satisfy the filing obligation of the registrant under any of the
following provisions:

|_| Written communications pursuant to Rule 425 under the Securities Act (17CFR
    230.425)

|_| Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17
    CFR240.14a-12)

|_| Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange
    Act (17 CFR 240.14d-2(b))

|_| Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange
    Act (17 CFR 240.13e-4(c))



Item 5.02      Departure of Directors or Principal Officers; Election of
               Directors; Appointment of Principal Officers.

               (b) On January 17, 2005, Ronald L. Skates, one of the company's
directors whose term will expire at the upcoming annual meeting of stockholders
on March 8, 2005, decided not to stand for re-election when his term expires in
March.


Item 1.01      Entry into a Material Definitive Agreement

               As a result of Mr. Skates' decision not to stand for re-election
to the company's Board of Directors, his term expires at this year's annual
meeting on March 8, 2005. Because this year's annual meeting date, and Mr.
Skates' termination of service date, is to occur one, two, three and four days,
respectively, ahead of the anniversary of prior annual meeting dates and the
dates upon which a total of 8,125 of Mr. Skates' options would otherwise vest,
on January 17, 2005, the company, pursuant to approval of the company's Board of
Directors and the Nominating and Corporate Governance Committee of the Board,
amended four option grant agreements between Mr. Skates and the company to
accelerate the vesting of these 8,125 options to March 8, 2005 that would have
otherwise vested on March 9, March 11, March 12 and March 13, 2005. At the time
of the amendment, all accelerated options had an option price greater than the
fair market value of the shares of the Corporation. All other unvested options
will terminate upon his termination of service on March 8, 2005.


Item 8.01      Other Events

               Mr. Robert J. Birgeneau has been nominated by the Board of
Directors to replace Mr. Skates as a Class II director, to stand for election at
the company's annual meeting of stockholders on March 8, 2005, with a term to
expire in 2008. Mr. Birgeneau is the Chancellor of the University of California,
Berkeley, and also holds a faculty appointment in the department of physics
there. Prior to assuming his current position, Mr. Birgeneau served as the
President of the University of Toronto. Prior to that, Mr. Birgeneau was the
Dean of the School of Science at the Massachusetts Institute of Technology, and
previously had been the chair of M.I.T.'s physics department. Mr. Birgeneau
received his B.Sc. in mathematics from the University of Toronto, and his Ph.D.
in physics from Yale University.


                                    SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned hereunto duly authorized.


                                CABOT MICROELECTRONICS CORPORATION


Date: January 21, 2005          By: /s/ WILLIAM S. JOHNSON
                                    ----------------------
                                    William S. Johnson
                                    Vice President and Chief Financial Officer
                                    [Principal Financial Officer]




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