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UNITED STATES
SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13G

Under the Securities Exchange Act of 1934
(Amendment No. _)*

SENORX, INC.

(Name of Issuer)

Common Stock

(Title of Class of Securities)

81724W 10 4

(CUSIP Number)

December 31, 2007

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

o Rule 13d-1(b)

o Rule 13d-1(c)

þ Rule 13d-1(d)

* The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.

The information required in the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).


CUSIP No.		81724W 10 4


1	NAME OF REPORTING PERSONS I.R.S. Identification No(s). of above person(s) (entities only) MPM BioVentures II, L.P.


2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
	(a) o
	(b) þ

3	SEC USE ONLY



4	CITIZENSHIP OR PLACE OF ORGANIZATION

	Delaware

		5	SOLE VOTING POWER

NUMBER OF			166,833

SHARES		6	SHARED VOTING POWER
BENEFICIALLY
OWNED BY			0

EACH		7	SOLE DISPOSITIVE POWER
REPORTING
PERSON			166,833

WITH:		8	SHARED DISPOSITIVE POWER

			0

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

	166,833

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)

	o

11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

	1.0%

12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

	PN

Page 2 of 18


CUSIP No.		81724W 10 4


1	NAME OF REPORTING PERSONS I.R.S. Identification No(s). of above person(s) (entities only) MPM BioVentures II-QP, L.P.


2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
	(a) o
	(b) þ

3	SEC USE ONLY



4	CITIZENSHIP OR PLACE OF ORGANIZATION

	Delaware

		5	SOLE VOTING POWER

NUMBER OF			1,511,814

SHARES		6	SHARED VOTING POWER
BENEFICIALLY
OWNED BY			0

EACH		7	SOLE DISPOSITIVE POWER
REPORTING
PERSON			1,511,814

WITH:		8	SHARED DISPOSITIVE POWER

			0

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

	1,511,814

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)

	o

11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

	8.8%

12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

	PN

Page 3 of 18


CUSIP No.		81724W 10 4


1	NAME OF REPORTING PERSONS I.R.S. Identification No(s). of above person(s) (entities only) MPM BioVentures GmbH & Co. Parallel-Beteiligungs KG


2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
	(a) o
	(b) þ

3	SEC USE ONLY



4	CITIZENSHIP OR PLACE OF ORGANIZATION

	Germany

		5	SOLE VOTING POWER

NUMBER OF			532,340

SHARES		6	SHARED VOTING POWER
BENEFICIALLY
OWNED BY			0

EACH		7	SOLE DISPOSITIVE POWER
REPORTING
PERSON			532,340

WITH:		8	SHARED DISPOSITIVE POWER

			0

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

	532,340

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)

	o

11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

	3.1%

12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

	PN

Page 4 of 18


CUSIP No.		81724W 10 4


1	NAME OF REPORTING PERSONS I.R.S. Identification No(s). of above person(s) (entities only) MPM Asset Management Investors 2001 LLC


2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
	(a) o
	(b) þ

3	SEC USE ONLY



4	CITIZENSHIP OR PLACE OF ORGANIZATION

	Delaware

		5	SOLE VOTING POWER

NUMBER OF			31,392

SHARES		6	SHARED VOTING POWER
BENEFICIALLY
OWNED BY			0

EACH		7	SOLE DISPOSITIVE POWER
REPORTING
PERSON			31,392

WITH:		8	SHARED DISPOSITIVE POWER

			0

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

	31,392

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)

	o

11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

	0.2%

12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

	OO

Page 5 of 18


CUSIP No.		81724W 10 4


1	NAME OF REPORTING PERSONS I.R.S. Identification No(s). of above person(s) (entities only) MPM Asset Management II, L.P.


2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
	(a) o
	(b) þ

3	SEC USE ONLY



4	CITIZENSHIP OR PLACE OF ORGANIZATION

	Delaware

		5	SOLE VOTING POWER

NUMBER OF			0

SHARES		6	SHARED VOTING POWER
BENEFICIALLY
OWNED BY			2,210,987*

EACH		7	SOLE DISPOSITIVE POWER
REPORTING
PERSON

WITH:		8	SHARED DISPOSITIVE POWER

			2,210,987*

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

	2,210,987*

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)

	o

11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

	12.9%

12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

	PN

* The shares are held as follows: 1,511,814 by MPM BioVentures II-QP, L.P. (“BV II QP”), 166,833 by MPM BioVentures II, L.P. (“BV II”) and 532,340 by MPM BioVentures GmbH & Co. Parallel-Beteiligungs KG (“BV KG”). The Reporting Person is the direct general partner of BV II QP, BV II and BV KG.

Page 6 of 18


CUSIP No.		81724W 10 4


1	NAME OF REPORTING PERSONS I.R.S. Identification No(s). of above person(s) (entities only) MPM Asset Management II LLC


2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
	(a) o
	(b) þ

3	SEC USE ONLY



4	CITIZENSHIP OR PLACE OF ORGANIZATION

	Delaware

		5	SOLE VOTING POWER

NUMBER OF			0

SHARES		6	SHARED VOTING POWER
BENEFICIALLY
OWNED BY			2,210,987*

EACH		7	SOLE DISPOSITIVE POWER
REPORTING
PERSON

WITH:		8	SHARED DISPOSITIVE POWER

			2,210,987*

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

	2,210,987*

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)

	o

11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

	12.9%

12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

	OO

* The shares are held as follows: 1,511,814 by MPM BioVentures II-QP, L.P. (“BV II QP”), 166,833 by MPM BioVentures II, L.P. (“BV II”) and 532,340 by MPM BioVentures GmbH & Co. Parallel-Beteiligungs KG (“BV KG”). The Reporting Person is indirect general partner of BV II QP, BV II and BV KG.

Page 7 of 18


CUSIP No.		81724W 10 4


1	NAME OF REPORTING PERSONS I.R.S. Identification No(s). of above person(s) (entities only) Ansbert Gadicke


2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
	(a) o
	(b) þ

3	SEC USE ONLY



4	CITIZENSHIP OR PLACE OF ORGANIZATION

	United States

		5	SOLE VOTING POWER

NUMBER OF			0

SHARES		6	SHARED VOTING POWER
BENEFICIALLY
OWNED BY			2,242,379*

EACH		7	SOLE DISPOSITIVE POWER
REPORTING
PERSON

WITH:		8	SHARED DISPOSITIVE POWER

			2,242,379*

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

	2,242,379*

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)

	o

11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

	13.0%

12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

	IN

* The shares are held as follows: 1,511,814 by MPM BioVentures II-QP, L.P. (“BV II QP”), 166,833 by MPM BioVentures II, L.P. (“BV II”), 31,392 by MPM Asset Management Investors 2001 LLC (“AM 2001”) and 532,340 by MPM BioVentures GmbH & Co. Parallel-Beteiligungs KG (“BV KG”). MPM Asset Management II, L.P. and MPM Asset Management II LLC (“AM II LLC”) are the direct and indirect general partners of BV II QP, BV II and BV KG. The Reporting Person is a member of AM II LLC and AM 2001. The Reporting Person disclaims beneficial ownership of all such shares except to the extent of his proportionate pecuniary interests therein.

Page 8 of 18


CUSIP No.		81724W 10 4


1	NAME OF REPORTING PERSONS I.R.S. Identification No(s). of above person(s) (entities only) Luke Evnin


2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
	(a) o
	(b) þ

3	SEC USE ONLY



4	CITIZENSHIP OR PLACE OF ORGANIZATION

	United States

		5	SOLE VOTING POWER

NUMBER OF			0

SHARES		6	SHARED VOTING POWER
BENEFICIALLY
OWNED BY			2,242,379*

EACH		7	SOLE DISPOSITIVE POWER
REPORTING
PERSON			0

WITH:		8	SHARED DISPOSITIVE POWER

			2,242,379*

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

	2,242,379*

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)

	o

11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

	13.0%

12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

	IN

Page 9 of 18


CUSIP No.		81724W 10 4


1	NAME OF REPORTING PERSONS I.R.S. Identification No(s). of above person(s) (entities only) Nicholas Galakatos


2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
	(a) o
	(b) þ

3	SEC USE ONLY



4	CITIZENSHIP OR PLACE OF ORGANIZATION

	United States

		5	SOLE VOTING POWER

NUMBER OF			0

SHARES		6	SHARED VOTING POWER
BENEFICIALLY
OWNED BY			2,242,379*

EACH		7	SOLE DISPOSITIVE POWER
REPORTING
PERSON			0

WITH:		8	SHARED DISPOSITIVE POWER

			2,242,379*

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

	2,242,379*

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)

	o

11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

	13.0%

12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

	IN

Page 10 of 18


CUSIP No.		81724W 10 4


1	NAME OF REPORTING PERSONS I.R.S. Identification No(s). of above person(s) (entities only) Michael Steinmetz


2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
	(a) o
	(b) þ

3	SEC USE ONLY



4	CITIZENSHIP OR PLACE OF ORGANIZATION

	United States

		5	SOLE VOTING POWER

NUMBER OF			0

SHARES		6	SHARED VOTING POWER
BENEFICIALLY
OWNED BY			2,242,379*

EACH		7	SOLE DISPOSITIVE POWER
REPORTING
PERSON			0

WITH:		8	SHARED DISPOSITIVE POWER

			2,242,379*

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

	2,242,379*

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)

	o

11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

	13.0%

12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

	IN

Page 11 of 18


CUSIP No.		81724W 10 4


1	NAME OF REPORTING PERSONS I.R.S. Identification No(s). of above person(s) (entities only) Kurt Wheeler


2	CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
	(a) o
	(b) þ

3	SEC USE ONLY



4	CITIZENSHIP OR PLACE OF ORGANIZATION

	United States

		5	SOLE VOTING POWER

NUMBER OF			0

SHARES		6	SHARED VOTING POWER
BENEFICIALLY
OWNED BY			2,242,379*

EACH		7	SOLE DISPOSITIVE POWER
REPORTING
PERSON			0

WITH:		8	SHARED DISPOSITIVE POWER

			2,242,379*

9	AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

	2,242,379*

10	CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)

	o

11	PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)

	13.0%

12	TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)

	IN

Page 12 of 18

Item 1.

	(a)		Name of Issuer

			SenoRx, Inc.

	(b)		Address of Issuer’s Principal Executive Offices
			11 Columbia, Suite A Aliso Viejo, California 92656

Item 2.

(a)

Name of Person Filing

MPM BioVentures II, LP
MPM BioVentures II-QP, L.P.
MPM BioVentures GmbH & Co. Parallel-Beteiligungs KG
MPM Asset Management Investors 2001 LLC
MPM Asset Management II, L.P.
MPM Asset Management II LLC
Ansbert Gadicke
Luke Evnin
Nicholas Galakatos
Michael Steinmetz
Kurt Wheeler

(b)

Address of Principal Business Office or, if none, Residence

c/o MPM Capital L.P.
The John Hancock Tower
200 Clarendon Street, 54^th Floor
Boston, MA 02116

(c)

Citizenship

All entities were organized in Delaware, except MPM BioVentures GmbH & Co. Parallel-Beteiligungs KG which was organized in Germany. The individuals are United States citizens.

(d)

Title of Class of Securities

Common Stock

(e)

CUSIP Number

81724W 10 4

Item 3. If this statement is filed pursuant to §§240.13d-1(b), or 240.13d-2(b) or (c), check whether the person filing is a:

Not applicable

Page 13 of 18

Item 4.

Ownership

(a)

Amount Beneficially Owned:


MPM BioVentures II, LP	166,833
MPM BioVentures II-QP, L.P.	1,511,814
MPM BioVentures GmbH & Co. Parallel-Beteiligungs KG	532,340
MPM Asset Management Investors 2001 LLC	31,392
MPM Asset Management II, L.P.	2,210,987	(1)
MPM Asset Management II LLC	2,210,987	(2)
Ansbert Gadicke	2,242,379	(3)
Luke Evnin	2,242,379	(3)
Nicholas Galakatos	2,242,379	(3)
Michael Steinmetz	2,242,379	(3)
Kurt Wheeler	2,242,379	(3)

Percent of Class:


MPM BioVentures II, LP	1.0	%
MPM BioVentures II-QP, L.P.	8.8	%
MPM BioVentures GmbH & Co. Parallel-Beteiligungs KG	3.1	%
MPM Asset Management Investors 2001 LLC	0.2	%
MPM Asset Management II, L.P.	12.9	%
MPM Asset Management II LLC	12.9	%
Ansbert Gadicke	13.0	%
Luke Evnin	13.0	%
Nicholas Galakatos	13.0	%
Michael Steinmetz	13.0	%
Kurt Wheeler	13.0	%

(b)

Number of shares as to which the person has:

(i)

Sole power to vote or to direct the vote


MPM BioVentures II, LP			166,833
MPM BioVentures II-QP, L.P.			1,511,814
MPM BioVentures GmbH & Co. Parallel-Beteiligungs KG			532,340
MPM Asset Management Investors 2001 LLC			31,392
MPM Asset Management II, L.P.			0
MPM Asset Management II LLC			0
Ansbert Gadicke			0
Luke Evnin			0
Nicholas Galakatos			0
Michael Steinmetz			0
Kurt Wheeler			0

Page 14 of 18

(ii) Shared power to vote or to direct the vote


MPM BioVentures II, LP	0
MPM BioVentures II-QP, L.P.	0
MPM BioVentures GmbH & Co. Parallel-Beteiligungs KG	0
MPM Asset Management Investors 2001 LLC	0
MPM Asset Management II, L.P.	2,210,987	(1)
MPM Asset Management II LLC	2,210,987	(2)
Ansbert Gadicke	2,242,379	(3)
Luke Evnin	2,242,379	(3)
Nicholas Galakatos	2,242,379	(3)
Michael Steinmetz	2,242,379	(3)
Kurt Wheeler	2,242,379	(3)

(iii)

Sole power to dispose or to direct the disposition of


MPM BioVentures II, LP			166,833
MPM BioVentures II-QP, L.P.			1,511,814
MPM BioVentures GmbH & Co. Parallel-Beteiligungs KG			532,340
MPM Asset Management Investors 2001 LLC			31,392
MPM Asset Management II, L.P.			0
MPM Asset Management II LLC			0
Ansbert Gadicke			0
Luke Evnin			0
Nicholas Galakatos			0
Michael Steinmetz			0
Kurt Wheeler			0

(iv)

Shared power to dispose or to direct the disposition of


MPM BioVentures II, LP	0
MPM BioVentures II-QP, L.P.	0
MPM BioVentures GmbH & Co. Parallel-Beteiligungs KG	0
MPM Asset Management Investors 2001 LLC	0
MPM Asset Management II, L.P.	2,210,987	(1)
MPM Asset Management II LLC	2,210,987	(2)
Ansbert Gadicke	2,242,379	(3)
Luke Evnin	2,242,379	(3)
Nicholas Galakatos	2,242,379	(3)
Michael Steinmetz	2,242,379	(3)
Kurt Wheeler	2,242,379	(3)


(1)		The shares are held as follows: 1,511,814 by MPM BioVentures II-QP, L.P. (“BV II QP”), 166,833 by MPM BioVentures II, L.P. (“BV II”) and 532,340 by MPM BioVentures GmbH & Co. Parallel-Beteiligungs KG (“BV KG”). The Reporting Person is the direct general partner of BV II QP, BV II and BV KG.

(2)		The shares are held as follows: 1,511,814 by BV II QP, 166,833 by BV II and 532,340 by BV KG. The Reporting Person is the indirect general partner of BV II QP, BV II and BV KG.

(3)		The shares are held as follows: 1,511,814 by BV II QP, 166,833 by BV II, 31,392 by MPM Asset Management Investors 2001 LLC (“AM 2001”) and 532,340 by BV KG. MPM Asset Management II, L.P. and MPM Asset Management II LLC (“AM II LLC”) are the direct and indirect general

Page 15 of 18

partners of BV II QP, BV II and BV KG. The Reporting Person is a member of AM II LLC and AM 2001. The Reporting Person disclaims beneficial ownership of all such shares except to the extent of his proportionate pecuniary interests therein.

Item 5. Ownership of Five Percent or Less of a Class

If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following o.

Item 6. Ownership of More than Five Percent on Behalf of Another Person

Not Applicable

Item 7. Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on By the Parent Holding Company or Control Person.

Not Applicable

Item 8. Identification and Classification of Members of the Group

Not Applicable

Item 9. Notice of Dissolution of a Group

Not Applicable

Item 10. Certification

Not Applicable

Page 16 of 18

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Dated: February 11, 2008


MPM BIOVENTURES II, L.P.		MPM BIOVENTURES II-QP, L.P.

By:	MPM Asset Management II, L.P., its General Partner	By:	MPM Asset Management II, L.P., its General Partner

By:	MPM Asset Management II LLC, its General Partner	By:	MPM Asset Management II LLC, its General Partner

By:	/s/ Luke Evnin	By:	/s/ Luke Evnin
	Name: Luke B. Evnin		Name: Luke B. Evnin
	Title: Investment Manager		Title: Investment Manager

MPM BIOVENTURES GMBH & CO. PARALLEL-BETEILIGUNGS KG		MPM ASSET MANAGEMENT INVESTORS 2001 LLC

		By:	/s/ Luke Evnin
By:	MPM Asset Management II LP, in its capacity as the Special Limited Partner		Name: Luke B. Evnin Title: Investment Manager

By:	MPM Asset Management II LLC, its General Partner

By:	/s/ Luke Evnin

	Name: Luke B. Evnin Title: Investment Manager

MPM ASSET MANAGEMENT II, L.P.		MPM ASSET MANAGEMENT II LLC

By:	MPM Asset Management II LLC, its General Partner

By:	/s/ Luke Evnin	By:	/s/ Luke Evnin

Name: Luke B. Evnin Title: Investment Manager		Name: Luke B. Evnin Title: Investment Manager

By:	/s/ Ansbert Gadicke	By:	/s/ Luke Evnin

	Name: Ansbert Gadicke		Name: Luke B. Evnin

By:	/s/ Nicholas Galakatos	By:	/s/ Michael Steinmetz

	Name: Nicholas Galakatos		Name: Michael Steinmetz

By:	/s/ Kurt Wheeler

	Name: Kurt Wheeler

EXHIBITS
A: Joint Filing Agreement

Page 17 of 18

EXHIBIT A

JOINT FILING AGREEMENT

In accordance with Rule 13d-1(k) under the Securities Exchange Act of 1934, as amended, the undersigned agree to the joint filing on behalf of each of them of a statement on Schedule 13G (including amendments thereto) with respect to the Common Stock of SenoRx, Inc. and further agree that this agreement be included as an exhibit to such filing. Each party to the agreement expressly authorizes each other party to file on its behalf any and all amendments to such statement. Each party to this agreement agrees that this joint filing agreement may be signed in counterparts.

In evidence whereof, the undersigned have caused this Agreement to be executed on their behalf this 11th day of February, 2008.


MPM BIOVENTURES II, L.P.		MPM BIOVENTURES II-QP, L.P.

By:	MPM Asset Management II, L.P., its General Partner	By:	MPM Asset Management II, L.P., its General Partner

By:	MPM Asset Management II LLC, its General Partner	By:	MPM Asset Management II LLC, its General Partner

By:	/s/ Luke Evnin	By:	/s/ Luke Evnin
	Name: Luke B. Evnin Title: Investment Manager		Name: Luke B. Evnin Title: Investment Manager

MPM BIOVENTURES GMBH & CO. PARALLEL-BETEILIGUNGS KG		MPM ASSET MANAGEMENT INVESTORS 2001 LLC

		By:	/s/ Luke Evnin
By:	MPM Asset Management II LP, in its capacity as the Special Limited Partner		Name: Luke B. Evnin Title: Investment Manager

By:	MPM Asset Management II LLC, its General Partner

By:	/s/ Luke Evnin

	Name: Luke B. Evnin Title: Investment Manager

MPM ASSET MANAGEMENT II, L.P.		MPM ASSET MANAGEMENT II LLC

By:	MPM Asset Management II LLC, its General Partner

By:	/s/ Luke Evnin	By:	/s/ Luke Evnin
Name: Luke B. Evnin Title: Investment Manager		Name: Luke B. Evnin Title: Investment Manager

By:	/s/ Ansbert Gadicke	By:	/s/ Luke Evnin
	Name: Ansbert Gadicke		Name: Luke B. Evnin

By:	/s/ Nicholas Galakatos	By:	/s/ Michael Steinmetz
	Name: Nicholas Galakatos		Name: Michael Steinmetz

By:	/s/ Kurt Wheeler
	Name: Kurt Wheeler

Page 18 of 18