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 or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person* Three Arch Management IV, L.L.C. (Last) (First) (Middle) 3200 ALPINE ROAD (Street) PORTOLA VALLEY CA 94028 (City) (State) (Zip)	2. Date of Event Requiring Statement (Month/Day/Year) 06/06/2006	3. Issuer Name and Ticker or Trading Symbol NORTH AMERICAN SCIENTIFIC INC [ NASI ]
		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 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 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	2,004,398	I	See Footnote(1)
Common Stock	44,258	I	See Footnote(2)
Common Stock	2,934,262	I	See Footnote(3)
Common Stock	138,720	I	See Footnote(4)

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: 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
Common Stock Warrant (Right to Buy)	(5)	06/06/2013	Common Stock	1,002,199	2.08	I	See Footnote(1)
Common Stock Warrant (Right to Buy)	(5)	06/06/2013	Common Stock	22,129	2.08	I	See Footnote(2)
Common Stock Warrant (Right to Buy)	(5)	06/06/2013	Common Stock	1,467,131	2.08	I	See Footnote(3)
Common Stock Warrant (Right to Buy)	(5)	06/06/2013	Common Stock	69,360	2.08	I	See Footnote(4)

1. Name and Address of Reporting Person* Three Arch Management IV, L.L.C. (Last) (First) (Middle) 3200 ALPINE ROAD (Street) PORTOLA VALLEY CA 94028 (City) (State) (Zip)

1. Name and Address of Reporting Person* THREE ARCH PARTNERS IV LP (Last) (First) (Middle) 3200 ALPINE ROAD (Street) PORTOLA VALLEY CA 94028 (City) (State) (Zip)

1. Name and Address of Reporting Person* THREE ARCH ASSOCIATES IV LP (Last) (First) (Middle) 3200 ALPINE ROAD (Street) PORTOLA VALLEY CA 94028 (City) (State) (Zip)

1. Name and Address of Reporting Person* WAN MARK A (Last) (First) (Middle) 3200 ALPINE ROAD (Street) PORTOLA VALLEY CA 94028 (City) (State) (Zip)

1. Name and Address of Reporting Person* JAEGER WILFRED E (Last) (First) (Middle) 3200 ALPINE ROAD (Street) PORTOLA VALLEY CA 94028 (City) (State) (Zip)

1. Name and Address of Reporting Person* NICHOLSON BARCLAY (Last) (First) (Middle) 3200 ALPINE ROAD (Street) PORTOLA VALLEY CA 94028 (City) (State) (Zip)

1. Name and Address of Reporting Person* TAC MANAGEMENT LLC (Last) (First) (Middle) 3200 ALPINE ROAD (Street) PORTOLA VALLEY CA 94028 (City) (State) (Zip)

1. Name and Address of Reporting Person* THREE ARCH CAPITAL LP (Last) (First) (Middle) 3200 ALPINE ROAD (Street) PORTOLA VALLEY CA 94028 (City) (State) (Zip)

1. Name and Address of Reporting Person* TAC ASSOCIATES LP (Last) (First) (Middle) 3200 ALPINE ROAD (Street) PORTOLA VALLEY CA 94028 (City) (State) (Zip)

Explanation of Responses:

1. The reportable securities are owned directly by Three Arch Partners IV, L.P. Three Arch Management IV, L.L.C. is the general partner of Three Arch Partners IV, L.P. Three Arch Management IV, L.L.C. disclaims beneficial ownership of these securities and this report shall not be deemed an admission that Three Arch Management IV, L.L.C. is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of its pecuniary interest therein. Mark A. Wan ("Wan"), Wilfred E. Jaeger ("Jaeger"), and Barclay Nicholson ("Nicholson"), are managing members of Three Arch Management IV, L.L.C. Each of Wan, Jaeger, and Nicholson disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any of them is the beneficial owner of such securities for purposes of Section 16 except to the extent of his or her pecuniary interest therein.

2. The reportable securities are owned directly by Three Arch Associates IV, L.P. Three Arch Management IV, L.L.C. is the general partner of Three Arch Associates IV, L.P. Three Arch Management IV, L.L.C. disclaims beneficial ownership of these securities and this report shall not be deemed an admission that Three Arch Management IV, L.L.C. is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of its pecuniary interest therein. Wan, Jaeger, and Nicholson are managing members of Three Arch Management IV, L.L.C. Each of Wan, Jaeger, and Nicholson disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any of them is the beneficial owner of such securities for purposes of Section 16 except to the extent of his or her pecuniary interest therein.

3. The reportable securities are owned directly by Three Arch Capital, L.P. TAC Management, L.L.C. is the general partner of Three Arch Capital, L.P. TAC Management, L.L.C. disclaims beneficial ownership of these securities and this report shall not be deemed an admission that TAC Management, L.L.C. is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of its pecuniary interest therein. Wan, Jaeger, and Nicholson are managing members of TAC Management, L.L.C. Each of Wan, Jaeger, and Nicholson disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any of them is the beneficial owner of such securities for purposes of Section 16 except to the extent of his or her pecuniary interest therein.

4. The reportable securities are owned directly by TAC Associates, L.P. TAC Management, L.L.C. is the general partner of TAC Associates, L.P. TAC Management, L.L.C. disclaims beneficial ownership of these securities and this report shall not be deemed an admission that TAC Management, L.L.C. is the beneficial owner of such securities for purposes of Section 16 or for any other purpose, except to the extent of its pecuniary interest therein. Wan, Jaeger, and Nicholson are managing members of TAC Management, L.L.C. Each of Wan, Jaeger, and Nicholson disclaims beneficial ownership of these securities and this report shall not be deemed an admission that any of them is the beneficial owner of such securities for purposes of Section 16 except to the extent of his or her pecuniary interest therein.

5. Immediately.

	/s/ Barclay Nicholson, Authorized Signatory	06/07/2006
	** Signature of Reporting Person	Date
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