FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person * SKATES RONALD L   2. Issuer Name and Ticker or Trading Symbol CABOT MICROELECTRONICS CORP [CCMP] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director _____ 10% Owner _____ Officer (give title below) _____ Other (specify below) (Last) (First) (Middle) C/O CABOT MICROELECTRONICS CORPORATION, 870 COMMONS DRIVE 3. Date of Earliest Transaction (Month/Day/Year) 01/29/2005 (Street) AURORA, IL 60504 4. If Amendment, Date Original Filed(Month/Day/Year) 6. Individual or Joint/Group Filing(Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock               2,560 D

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Phantom Stock

$ 27.45

07/21/2004

07/21/2004

Common Stock

36.4299

36.4299

D

Phantom Stock

$ 28.05

06/14/2004

06/14/2004

Common Stock

71.3012

71.3012

D

Phantom Stock

$ 34.3

09/28/2004

09/28/2004

Common Stock

87.4636

87.4636

D

Phantom Stock

$ 34.39

08/23/2004

08/23/2004

Common Stock

29.0782

29.0782

D

Phantom Stock

$ 36.5

10/06/2004

10/06/2004

Common Stock

27.3973

27.3973

D

Phantom Stock

$ 37.8

11/29/2004

11/29/2004

Common Stock

26.455

26.455

D

Phantom Stock

$ 39.18

12/07/2004

12/07/2004

Common Stock

76.5697

76.5697

D

Phantom Stock

$ 42.44

03/09/2004

03/09/2004

Common Stock

518.3789

518.3789

D

Phantom Stock

$ 50.1

12/08/2003

12/08/2003

Common Stock

59.8802

59.8802

D

Phantom Stock

$ 50.95

06/18/2003

06/17/2003

Common Stock

1,513.9321

1,513.9321

D

Phantom Stock

$ 52.5

11/05/2003

11/05/2003

Common Stock

19.0476

19.0476

D

Phantom Stock

$ 55.37

11/03/2003

11/03/2003

Common Stock

162.5429

162.5429

D

Phantom Stock

$ 59.05

09/23/2003

09/23/2003

Common Stock

50.8044

50.8044

D

Phantom Stock

$ 30.43

01/29/2005

01/31/2005

J(1)

32.8623

01/29/2005

01/29/2005(2)

Common Stock

32.8623

$ 0

32.8623

D

Stock Options (Right to buy)

$ 38.34

03/11/2004

03/11/2013

Common Stock

7,500

7,500

D

Stock Options (Right to buy)

$ 42.44

03/09/2005

03/09/2014

Common Stock

10,000

10,000

D

Stock Options (Right to buy)

$ 46.875

03/13/2002

03/13/2008

Common Stock

7,500

7,500

D

Stock Options (Right to buy)

$ 65.73

03/12/2003

03/12/2012

Common Stock

7,500

7,500

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
SKATES RONALD L C/O CABOT MICROELECTRONICS CORPORATION 870 COMMONS DRIVE AURORA, IL 60504	X

Signatures

H. Carol Bernstein (Power of Attorney)		02/01/2005
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(2)	Rights to aquire shares pursuant to Directors' Deferred Compensation Plan are already earned.
(1)	Rights to acquire shares pursuant to Directors' Deferred Compensation Plan adopted March 12, 2001 as amended June 17, 2003.

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