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):
                                  July 24, 2003


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



                                                                   

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



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

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

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







Item 7.  Financial Statements and Exhibits.

         (c)      Exhibits

                  The following exhibits are filed herewith:

                  99.1     Press release, dated July 24, 2003, entitled "Cabot
                           Microelectronics Reports Results For Third Fiscal
                           Quarter 2003."

Item 9.  Regulation FD Disclosure (Item 12. Results of Operations and Financial
         Condition).

         On July 24, 2003, Cabot Microelectronics Corporation issued a press
release entitled "Cabot Microelectronics Reports Results For Third Fiscal
Quarter 2003," 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 third fiscal quarter ended June 30,
2003. 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 under Item 12 of Form 8-K and is being presented under Item 9 in
accordance with the Commission's interim guidance regarding Form 8-K Item 11 and
Item 12 filing requirements, as set forth in Release No. 33-8216. This
information 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.



                                    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: July 24, 2003              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 July 24, 2003, entitled
                    "Cabot Microelectronics Reports Results For Third Fiscal
                    Quarter 2003."






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