SEC Form 4

FORM 4		UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940	OMB APPROVAL OMB Number: 3235-0287 Estimated average burden hours per response: 0.5
	Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person* Charles River Partnership XIII, LP (Last) (First) (Middle) C/O CHARLES RIVER VENTURES ONE BROADWAY, 15TH FLOOR (Street) CAMBRIDGE MA 02142 (City) (State) (Zip)	2. Issuer Name and Ticker or Trading Symbol Millennial Media Inc. [ MM ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director X 10% Owner Officer (give title below) Other (specify below)
	3. Date of Earliest Transaction (Month/Day/Year) 04/03/2012
	4. If Amendment, Date of Original Filed (Month/Day/Year)	6. Individual or Joint/Group Filing (Check Applicable Line) Form filed by One Reporting Person X Form filed by More than One Reporting Person

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	04/03/2012		C		10,362,712(1)	A	(2)	10,362,712(1)	I	By Funds(3)(4)

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 Securities Underlying Derivative Security (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: 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
Series B Convertible Preferred Stock	(2)	04/03/2012		C			7,612,115(5)	(2)	(2)	Common Stock	7,612,115(5)	$0.00	0	I	By Funds(4)
Series C Convertible Preferred Stock	(2)	04/03/2012		C			896,636(6)	(2)	(2)	Common Stock	896,636(6)	$0.00	0	I	By Funds(4)
Series D Convertible Preferred Stock	(2)	04/03/2012		C			1,853,961(7)	(2)	(2)	Common Stock	1,853,961(7)	$0.00	0	I	By Funds(4)

1. Name and Address of Reporting Person* Charles River Partnership XIII, LP (Last) (First) (Middle) C/O CHARLES RIVER VENTURES ONE BROADWAY, 15TH FLOOR (Street) CAMBRIDGE MA 02142 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* Charles River Friends XIII-A LP (Last) (First) (Middle) C/O CHARLES RIVER VENTURES ONE BROADWAY, 15TH FLOOR (Street) CAMBRIDGE MA 02142 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* Charles River XIII GP, LLC (Last) (First) (Middle) C/O CHARLES RIVER VENTURES ONE BROADWAY, 15TH FLOOR (Street) CAMBRIDGE MA 02142 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* Charles River XIII GP, LP (Last) (First) (Middle) C/O CHARLES RIVER VENTURES ONE BROADWAY, 15TH FLOOR (Street) CAMBRIDGE MA 02142 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

Explanation of Responses:

1. The total represents shares received upon conversion of shares of Series B, Series C and Series D convertible preferred stock.

2. Effective upon the closing of the issuer's initial public offering of its common stock, each share of convertible preferred stock automatically converted into one share of common stock. The convertible preferred stock had no expiration date.

3. The total includes 10,079,791 shares held by Charles River Partnership XIII, LP ("CRP XIII") and 282,921 shares held by Charles River Friends XIII-A, LP ("CRF XIII-A").

4. Charles River XIII GP, LP ("CR XIII GP, LP") is the general partner of CRP XIII. Charles River XIII GP, LLC ("CR XIII GP, LLC") is the general partner of both CRF XIII-A and Charles River XIII GP, LP. Each of CR XIII GP, LP and CR XIII GP, LLC may be deemed to beneficially own the reported securities, but each disclaims beneficial ownership of such reported securities except to the extent of its pecuniary interest therein. The filing of this statement by any reporting person shall not be deemed an admission that such person is, for purposes of Section 16 of the Securities Exchange Act of 1934 or otherwise, the beneficial owner of any equity securities covered by this statement.

5. The total includes 7,404,290 shares held by CRP XIII and 207,825 shares held by CRF XIII-A.

6. The total includes 872,156 shares held by CRP XIII and 24,480 shares held by CRF XIII-A.

7. The total includes 1,803,345 shares held by CRP XIII and 50,616 shares held by CRF XIII-A.

Remarks:

	/s/ Sarah Reed, Attorney-in-fact for Charles River Partnership XIII, LP	04/03/2012
	/s/ Sarah Reed, Attorney-in-fact for Charles River Friends XIII-A, LP	04/03/2012
	/s/ Sarah Reed, Attorney-in-fact for Charles River XIII GP, LLC	04/03/2012
	/s/ Sarah Reed, Attorney-in-fact for Charles River XIII GP, LP	04/03/2012
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
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