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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1. Name and Address of Reporting Person * ONeil Mark F   2. Issuer Name and Ticker or Trading Symbol DealerTrack Holdings, Inc. [TRAK] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) __X__ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) Chairman of Board, Pres. & CEO (Last) (First) (Middle) C/O DEALERTRACK HOLDINGS, INC., 1111 MARCUS AVENUE, SUITE M04 3. Date of Earliest Transaction (Month/Day/Year) 12/16/2005 (Street) LAKE SUCCESS, NY 11042 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 12/16/2005   C   34,121 A (1) 139,121 (2) D   Common Stock 12/16/2005   C   1,164 A (3) 151,164 (4) I By Spouse, as a limited partner of GRP II Partners, L.P. (5)

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

Convertible Series C-2 Preferred Stock

(1)

12/16/2005

C

33,921

(1)

(1)

Common Stock

34,121

(1)

0

D

Convertible Series C-1 Preferred Stock

(3)

12/16/2005

C

1,103

(3)

(3)

Common Stock

1,164

(3)

0

I

By Spouse, as a limited partner of GRP II Partners, L.P. (6)

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
ONeil Mark F C/O DEALERTRACK HOLDINGS, INC. 1111 MARCUS AVENUE, SUITE M04 LAKE SUCCESS, NY 11042	X		Chairman of Board, Pres. & CEO

Signatures

/s/ Eric D. Jacobs as attorney-in-fact for Mark F. O'Neil		12/20/2005
**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).
(1)	Shares of Convertible Series C-2 Preferred Stock were automatically converted into shares of common stock on a 1-to-1.0059 basis upon the closing of the Issuer's initial public offering on December 16, 2005.
(2)	Includes 30,000 shares of restricted common stock held directly by Mr. O'Neil, and excludes a total of 151,164 shares of common stock held indirectly by Mr. O'Neil, as initially disclosed on Mr. O'Neil's Form 3.
(3)	Shares of Convertible Series C-1 Preferred Stock were automatically converted into shares of common stock on a 1-to-1.0555 basis upon the closing of the Issuer's initial public offering on December 16, 2005.
(4)	Includes 100,000 shares of common stock held indirectly by Mr. O'Neil as Trustee for the Mark F. O'Neil Qualified Grantor Retained Annuity Trust, and 50,000 shares of common stock held indirectly by Mr. O'Neil, which shares are held directly by Mr. O'Neil's spouse, as initially disclosed on Mr. O'Neil's Form 3.
(5)	The shares are held by GRP II Partners, L.P. Monique O'Neil, the spouse of Mark O'Neil, is a limited partner of GRP II Partners, L.P. Through this partnership interest, she has an indirect economic interest in 1,164 shares of common stock.
(6)	The shares of Convertible Series C-1 Preferred Stock were held by GRP II Partners, L.P. Monique O'Neil, the spouse of Mark O'Neil, is a limited partner of GRP II Partners, L.P. Through this partnership interest, she had an indirect economic interest in approximately 1,103 shares of Convertible Series C-1 Preferred Stock, which automatically converted into 1,164 shares of common stock upon the closing of the Issuer's initial public offering.

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