FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 INITIAL STATEMENT OF 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 *   MPM BIOVENTURES III LLC 2. Date of Event Requiring Statement (Month/Day/Year) 04/26/2007 3. Issuer Name and Ticker or Trading Symbol Pharmasset Inc [VRUS] (Last) (First) (Middle) C/O MPM ASSET MANAGEMENT, 200 CLARENDON ST., 54TH FLOOR 4. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director __X__ 10% Owner _____ Officer (give title below) _____ Other (specify below) 5. If Amendment, Date Original Filed(Month/Day/Year) (Street) BOSTON, MA 02116 6. Individual or Joint/Group Filing(Check Applicable Line) ___ Form filed by One Reporting Person _X_ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Beneficially Owned

1.Title of Security (Instr. 4) 2. Amount of Securities Beneficially Owned (Instr. 4) 3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5) 4. Nature of Indirect Beneficial Ownership (Instr. 5) Common Stock 830,823 I See Footnote (1)

Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.			SEC 1473 (7-02)
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Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Warrant to purchase Series D-1 Preferred Stock	  (2)	  (2)	Common Stock	215,687	$ 1.5	I	See Footnote (3)
Series D Preferred Stock	  (4)	  (4)	Common Stock	607,085	$ (4)	I	See Footnote (5)

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
MPM BIOVENTURES III LLC C/O MPM ASSET MANAGEMENT 200 CLARENDON ST., 54TH FLOOR BOSTON, MA 02116	Â	  X	Â	Â
MPM BIOVENTURES III PARALLEL FUND, LP C/O MPM ASSET MANAGEMENT 200 CLARENDON ST., 54TH FLOOR BOSTON, MA 02116	Â	  X	Â	Â
MPM BIOVENTURES III GMBH & CO. Beteiligungs KG C/O MPM ASSET MANAGEMENT 200 CLARENDON ST., 54TH FLOOR BOSTON, MA 02116	Â	  X	Â	Â
MPM BIOVENTURES III LP C/O MPM ASSET MANAGEMENT 200 CLARENDON ST., 54TH FLOOR BOSTON, MA 02116	Â	  X	Â	Â
MPM BIOVENTURES III GP LP C/O MPM ASSET MANAGEMENT 200 CLARENDON ST., 54TH FLOOR BOSTON, MA 02116	Â	  X	Â	Â
MPM BIOVENTURES III QP LP C/O MPM ASSET MANAGEMENT 200 CLARENDON ST., 54TH FLOOR BOSTON, MA 02116	Â	  X	Â	Â
MPM Asset Management Investors 2004 BVIII LLC C/O MPM ASSET MANAGEMENT 200 CLARENDON ST., 54TH FLOOR BOSTON, MA 02116	Â	  X	Â	Â

Signatures

/s/ Luke Evnin, Series A Member of MPM BioVentures III LLC		04/26/2007
**Signature of Reporting Person		Date
/s/ Luke Evnin, Series A Member of MPM BioVentures III LLC, the general partner of MPM BioVentures III GP, LP, the general partner of MPM BioVentures III Parallel Fund, LP		04/26/2007
**Signature of Reporting Person		Date
/s/ Luke Evnin, Series A Member of MPM BioVentures III LLC, the general partner of MPM BioVentures III GP, LP, in its capacity as the Managing Limited Partner of MPM BioVentures III GmbH & Co. Beteiligungs KG		04/26/2007
**Signature of Reporting Person		Date
/s/ Luke Evnin, Series A Member of MPM BioVentures III LLC, the general partner of MPM BioVentures III GP, LP, the general partner of MPM BioVentures III, LP		04/26/2007
**Signature of Reporting Person		Date
/s/ Luke Evnin, Series A Member of MPM BioVentures III LLC, the general partner of MPM BioVentures III GP, LP		04/26/2007
**Signature of Reporting Person		Date
/s/ Luke Evnin, Series A Member of MPM BioVentures III LLC, the general partner of MPM BioVentures III GP, LP, the general partner of MPM BioVentures III-QP, LP		04/26/2007
**Signature of Reporting Person		Date
/s/ Luke Evnin, manager of MPM Asset Management Investors 2004 BVIII LLC		04/26/2007
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 5(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)	These shares are held as follows: 46,335 shares by MPM BioVentures III, L.P., ("BV III"), 689,062 shares by MPM BioVentures III-QP, L.P. ("BV III QP"), 58,233 shares held by MPM BioVentures III GmbH & Co. Beteiligungs KG ("BV KG"), 20,812 shares by MPM BioVentures III Parallel Fund, L.P. ("BV III PF") and 16,381 shares held by MPM Asset Management Investors 2004 BVIII LLC ("AM BV III"). MPM BioVentures III GP, L.P. ("BV III GP") and MPM BioVentures III LLC ("BV III LLC") are the direct and indirect general partners of BV III, BV III QP, BV III PF and BV KG. Nicholas Galakatos, Dennis Henner, Nicholas Simon, III and Kurt Wheeler are members of BV III LLC and AM BV III. Each member of the group disclaims beneficial ownership of all such shares except to the extent of their respective proportionate pecuniary interests therein.
(2)	Immediately exercisable. These warrants shall expire upon the closing of the Issuer's initial public offering.
(3)	The shares, on a post-conversion basis, are held as follows: 12,029 by BV III, 178,885 by BV III QP, 15,117 by BV KG, 5,403 by BV III PF and 4,253 by AM BV III. Each member of the group disclaims beneficial ownership of all such shares except to the extent of their respective proportionate pecuniary interests therein.
(4)	Each share of preferred stock will convert automatically on a .666667 for 1 basis into shares of Common Stock upon the closing of the Issuer's initial public offering.
(5)	The shares, on a post-conversion basis, are held as follows: 33,857 by BV III, 503,500 by BV III QP, 42,551 by BV KG, 15,207 by BV III PF and 11,970 by AM BV III. Each member of the group disclaims beneficial ownership of all such shares except to the extent of their respective proportionate pecuniary interests therein.
  Remarks: See Form 3 for Nicholas Simon, III for additional members of the joint filing.

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