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

                                   FORM 10-K/A

                               AMENDMENT NO. 1 TO
                [X] ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d)
                     OF THE SECURITIES EXCHANGE ACT OF 1934

                  FOR THE FISCAL YEAR ENDED SEPTEMBER 30, 2002
                                       OR
            [ ] TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF
                       THE SECURITIES EXCHANGE ACT OF 1934

               FOR THE TRANSITION PERIOD FROM ________ TO ________

                        COMMISSION FILE NUMBER 000-30205

                       CABOT MICROELECTRONICS CORPORATION
             (Exact name of registrant as specified in its charter)

                DELAWARE                                 36-4324765
        (State of Incorporation)                     (I.R.S. Employer
                                                    Identification No.)

        870 NORTH COMMONS DRIVE                            60504
            AURORA, ILLINOIS                            (Zip Code)
(Address of principal executive offices)

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

Securities registered pursuant to Section 12(b) of the Act: None

Securities registered pursuant to Section 12(g) of the Act: Common Stock, $0.001
                                                            par value

Indicate by check mark whether the registrant: (1) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Exchange Act of
1934 during the preceding 12 months (or for such shorter period that the
registrant was required to file such reports), and (2) has been subject to such
filing requirements for the past 90 days. YES  X   NO
                                              ---     ---

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405
of Regulation S-K is not contained herein, and will not be contained, to the
best of registrant's knowledge, in definitive proxy or information statements
incorporated by reference in Part III of this Form 10-K or any amendment to this
Form 10-K. [X]

Indicate by check mark whether the registrant is an accelerated filer (as
defined in Exchange Act Rule 12b-2 ). YES  X   NO
                                          ---     ---

The aggregate market value of the registrant's Common Stock held beneficially or
of record by stockholders who are not affiliates of the registrant, based upon
the closing price of the Common Stock on November 29, 2002 as reported by the
Nasdaq National Market, was approximately $1,469,000,000. For the purposes
hereof, "affiliates" include all executive officers and directors of the
registrant.

As of November 29, 2002, the Company had 24,334,559 shares of Common Stock
outstanding.

                       DOCUMENTS INCORPORATED BY REFERENCE

Portions of the registrant's definitive Proxy Statement for the Annual Meeting
of Stockholders to be held on March 11, 2003 are incorporated by reference in
Part III of this Form 10-K to the extent stated herein. This Form 10-K includes
statements that constitute "forward-looking statements" within the meaning of
federal securities regulations. For more detail regarding "forward-looking
statements" see item 7 of Part II of this Form 10-K






EXPLANATORY NOTE

     Cabot Microelectronics Corporation filed its original Annual Report on Form
10-K for the fiscal year ended September 30, 2002 on December 10, 2002. This
Amendment No. 1 on Form 10-K/A is filed solely to amend Part III, Item 12 for
the purpose of including the Equity Compensation Plan Information tabular
disclosure which was inadvertently omitted from our Annual Report on Form 10-K.
This information is required to be filed pursuant to Item 201(d) of Regulation
S-K. No attempt has been made in this Amendment No. 1 on Form 10-K/A to modify
or update disclosures for events which occurred subsequent to the original
filing.


PART III

ITEM 12. SECURITY OWNERSHIP OF CERTAIN BENEFICIAL OWNERS AND MANAGEMENT AND
RELATED STOCKHOLDER MATTERS

EQUITY COMPENSATION PLAN INFORMATION

     Shown below is information as of September 30, 2002 with respect to the
shares of common stock that may be issued under Cabot Microelectronics' existing
equity compensation plans.




                                       (a)                        (b)                               (c)
                             Number of securities
                             to be issued upon           Weighted-average          Number of securities remaining
                             exercise of                 exercise price of         available for future issuance under
                             outstanding options,        outstanding options,      equity compensation plans (excluding
     Plan category           warrants and rights         warrants and rights       securities reflected in column (a))
- -------------------------    ------------------------    ----------------------    --------------------------------------
                                                                          
Equity compensation
plans approved by
security holders                    2,818,887                   $48.64                           3,492,497 (1)

Equity compensation
plans not approved by
security holders                        --                        --                                 --
                                    ---------                   ------                           ---------
Total                               2,818,887                   $48.64                           3,492,497
                                    ---------                   ------                           ---------



     (1)  Includes 368,962 shares available for future issuance under our
          Employee Stock Purchase Plan.


     The other information required by Item 12 of Form 10-K is incorporated by
reference from the information contained in the section captioned "Stock
Ownership" in the Proxy Statement.


                                       2




                                   SIGNATURES

     Pursuant to the requirements of section 13 or 15(d) of the Securities
Exchange Act of 1934, the registrant has duly caused this report to be signed on
its behalf by the undersigned thereunto duly authorized:



                                             CABOT MICROELECTRONICS CORPORATION
                                             (Registrant)

Date: May 13, 2003                           /s/ MATTHEW NEVILLE
                                             -----------------------------------
                                             Matthew Neville
                                             Chairman of the Board, President
                                             and Chief Executive Officer
                                             [Principal Executive Officer]


Date: May 13, 2003                           /s/ WILLIAM S. JOHNSON
                                             -----------------------------------
                                             William S. Johnson
                                             Vice President and Chief Financial
                                             Officer
                                             [Principal Financial Officer]


Date: May 13, 2003                           /s/ DANIEL S. WOBBY
                                             -----------------------------------
                                             Daniel S. Wobby
                                             Corporate Controller
                                             [Principal Accounting Officer]


     Pursuant to the requirements of the Securities Exchange Act of 1934, this
report has been signed below by the following persons on behalf of the
registrant and in the capacities and on the dates indicated:


Date: May 13, 2003                           /s/ MATTHEW NEVILLE
                                             -----------------------------------
                                             Matthew Neville
                                             Chairman of the Board, President
                                             and Chief Executive Officer
                                             [Director]


Date: May 13, 2003                           /s/ JUAN ENRIQUEZ-CABOT*
                                             -----------------------------------
                                             Juan Enriquez-Cabot
                                             [Director]


Date: May 13, 2003                           /s/ JOHN P. FRAZEE, JR.*
                                             -----------------------------------
                                             John P. Frazee, Jr.
                                             [Director]


Date: May 13, 2003                           /s/ H. LAURANCE FULLER*
                                             -----------------------------------
                                             H. Laurance Fuller
                                             [Director]


Date: May 13, 2003                           /s/ J. JOSEPH KING*
                                             -----------------------------------
                                             J. Joseph King
                                             [Director]



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Date: May 13, 2003                           /s/ RONALD L. SKATES*
                                             -----------------------------------
                                             Ronald L. Skates
                                             [Director]


Date: May 13, 2003                           /s/ STEVEN V. WILKINSON*
                                             -----------------------------------
                                             Steven V. Wilkinson
                                             [Director]



* by H. Carol Bernstein as Attorney-in-fact pursuant to the requirements of
section 13 or 15(d) of the Securities Exchange Act of 1934, pursuant to Power of
Attorney filed as Exhibit 24.1 to registrant's original Annual Report on Form
10-K for the fiscal year ended September 30, 2002, which was filed on December
10, 2002.



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                                 CERTIFICATIONS

I, Matthew Neville, Chief Executive Officer of Cabot Microelectronics
Corporation, certify that:

         1. I have reviewed this Amendment No. 1 on Form 10-K/A to Annual Report
on Form 10-K (the "Amendment") of Cabot Microelectronics Corporation;

         2. Based on my knowledge, this Amendment does not contain any untrue
statement of a material fact or omit to state a material fact necessary to make
the statements made, in light of the circumstances under which such statements
were made, not misleading with respect to the period covered by this Amendment;

         3. Based on my knowledge, the financial statements, and other financial
information included in this Amendment, fairly present in all material respects
the financial condition, results of operations and cash flows of the registrant
as of, and for, the periods presented in this Amendment;

         4. The registrant's other certifying officer and I are responsible for
establishing and maintaining disclosure controls and procedures (as defined in
Exchange Act Rules 13a-14 and 15d-14) for the registrant and we have:

            a) Designed such disclosure controls and procedures to ensure that
material information relating to the registrant, including its consolidated
subsidiaries, is made known to us by others within those entities, particularly
during the period in which this Amendment is being prepared;

            b) Evaluated the effectiveness of the registrant's disclosure
controls and procedures as of a date within 90 days prior to the filing date of
this Amendment (the "Evaluation Date"); and

            c) Presented in the Quarterly Report on Form 10-Q being filed
simultaneously herewith our conclusions about the effectiveness of the
disclosure controls and procedures based on our evaluation as of the Evaluation
Date;

         5. The registrant's other certifying officer and I have disclosed,
based on our most recent evaluation, to the registrant's auditors and the audit
committee of registrant's board of directors;

            a) All significant deficiencies in the design or operation of
internal controls which could adversely affect the registrant's ability to
record, process, summarize and report financial data and have identified for the
registrant's auditors any material weaknesses in internal controls; and

            b) Any fraud, whether or not material, that involves management or
other employees who have a significant role in the registrant's internal
controls; and

         6. The registrant's other certifying officer and I have indicated in
the Quarterly Report on Form 10-Q being filed simultaneously herewith whether or
not there were significant changes in internal controls or in other factors that
could significantly affect internal controls subsequent to the date of our most
recent evaluation, including any corrective actions with regard to significant
deficiencies and material weaknesses.


Date: May 13, 2003                           /s/ MATTHEW NEVILLE
                                             -----------------------------------
                                             Matthew Neville
                                             Chief Executive Officer




                                       5



                                 CERTIFICATIONS


I, William S. Johnson, Chief Financial Officer of Cabot Microelectronics
Corporation, certify that:

         1. I have reviewed this Amendment No. 1 on Form 10-K/A to Annual Report
on Form 10-K (the "Amendment") of Cabot Microelectronics Corporation;

         2. Based on my knowledge, this Amendment does not contain any untrue
statement of a material fact or omit to state a material fact necessary to make
the statements made, in light of the circumstances under which such statements
were made, not misleading with respect to the period covered by this Amendment;

         3. Based on my knowledge, the financial statements, and other financial
information included in this Amendment, fairly present in all material respects
the financial condition, results of operations and cash flows of the registrant
as of, and for, the periods presented in this Amendment;

         4. The registrant's other certifying officer and I are responsible for
establishing and maintaining disclosure controls and procedures (as defined in
Exchange Act Rules 13a-14 and 15d-14) for the registrant and we have:

            a) Designed such disclosure controls and procedures to ensure that
material information relating to the registrant, including its consolidated
subsidiaries, is made known to us by others within those entities, particularly
during the period in which this Amendment is being prepared;

            b) Evaluated the effectiveness of the registrant's disclosure
controls and procedures as of a date within 90 days prior to the filing date of
this Amendment (the "Evaluation Date"); and

            c) Presented in the Quarterly Report on Form 10-Q being filed
simultaneously herewith our conclusions about the effectiveness of the
disclosure controls and procedures based on our evaluation as of the Evaluation
Date;

         5. The registrant's other certifying officer and I have disclosed,
based on our most recent evaluation, to the registrant's auditors and the audit
committee of registrant's board of directors;

            a) All significant deficiencies in the design or operation of
internal controls which could adversely affect the registrant's ability to
record, process, summarize and report financial data and have identified for the
registrant's auditors any material weaknesses in internal controls; and

            b) Any fraud, whether or not material, that involves management or
other employees who have a significant role in the registrant's internal
controls; and

         6. The registrant's other certifying officer and I have indicated in
the Quarterly Report on Form 10-Q being filed simultaneously herewith whether or
not there were significant changes in internal controls or in other factors that
could significantly affect internal controls subsequent to the date of our most
recent evaluation, including any corrective actions with regard to significant
deficiencies and material weaknesses.


Date: May 13, 2003                           /s/ WILLIAM S. JOHNSON
                                             -----------------------------------
                                             William S. Johnson
                                             Chief Financial Officer


                                       6



EXHIBIT LIST

         99.1   Certification Pursuant to 18 U.S.C. Section 1350, as Adopted
                Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 dated
                May 13, 2003.

         99.2   Certification Pursuant to 18 U.S.C. Section 1350, as Adopted
                Pursuant to Section 906 of the Sarbanes-Oxley Act of 2002 dated
                May 13, 2003.


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