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):
                                 April 28, 2005


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


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


                    870 Commons Drive, Aurora, Illinois 60504
              -----------------------------------------------------
               (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
          (17 CFR 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 2.02     Results of Operations and Financial Condition.

         On April 28, 2005, Cabot Microelectronics Corporation issued a press
release entitled "Cabot Microelectronics Reports Results For Second Quarter of
Fiscal 2005," a copy of which is attached hereto as Exhibit 99.1 and
incorporated herein by reference. The press release contains financial and other
information including that related to our second fiscal quarter ended March 31,
2005. The press release also includes cautionary statements identifying
important factors that could cause actual results to differ materially from
those described by any forward-looking statements.

         This information is being furnished pursuant to Item 2.02 of Form 8-K
and shall not be deemed "filed" for purposes of Section 18 of the Securities and
Exchange Act of 1934, as amended (the "Exchange Act"), or incorporated by
reference in any filing under the Securities Act of 1933, as amended, or the
Exchange Act, except as shall be expressly set forth by specific reference in
such a filing.


Item 9.01     Financial Statements and Exhibits.

              (c)   Exhibits

                    The following exhibit is being furnished, not filed,
                    herewith pursuant to Item 2.02 of Form 8-K:

                    99.1  Press release, dated April 28, 2005, entitled "Cabot
                    Microelectronics Reports Results For Second Quarter of
                    Fiscal 2005."


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                                    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: April 28, 2005                    By: /s/ WILLIAM S. JOHNSON
                                            ----------------------
                                            William S. Johnson
                                            Vice President and Chief Financial
                                            Officer
                                            [Principal Financial Officer]




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                                INDEX TO EXHIBITS

Exhibit
Number              Title
------              -----


99.1                Press release, dated April 28, 2005, entitled "Cabot
                    Microelectronics Reports Results For Second Quarter of
                    Fiscal 2005."





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