The purchase price is equal to $0.246 per Security, of which $0.01 is allocated to the Warrants. The purchase price represents a 40% discount to the volume weighted average price of the Common Stock on the Nasdaq Global Market, as reported by Bloomberg Financial Markets, for the 20 trading day period ending on the trading day immediately preceding the date of the Securities Purchase Agreement. The Warrants have an exercise price of $0.246 per share, subject to certain adjustments. The Warrants may be exercised no earlier than 180 days from the closing date of the transaction and will expire seven years from the date of issuance.

In order to close the Private Placement, the Company must obtain stockholder approval of the Private Placement and the amendment of its Certificate of Incorporation to increase the number of shares of Common Stock it is authorized to issue. The Securities Purchase Agreement requires that the Company file a preliminary proxy statement, information statement or consent statement with the Securities and Exchange Commission (the “Commission”) to solicit stockholder approval by December 19, 2007. The Company expects to close the Private Placement as soon as practicable after it obtains stockholder approval.

The Investors have agreed to purchase the following amounts of Securities in the offering:

Three Arch Partners currently owns 5,121,638 shares of Common Stock. If the transaction is consummated, Three Arch Partners’ percentage ownership of the outstanding Common Stock will increase from approximately 17.3% to 49.4% (and 43.9% of the Common Stock on a fully diluted basis).

The net proceeds to the Company of the Private Placement after payment of fees and expenses are expected to be approximately $14,115,000. The terms of the Private Placement were approved by a committee of the Company’s Board of Directors consisting only of disinterested directors. The Company’s directors and executive officers have executed lock-up agreements restricting their ability to sell shares of the Common Stock for 180 days following the closing of the transaction. The Investors will be required to enter into such lock-up agreements prior to the closing of the transaction.

CIBC World Markets Corp. is acting as sole placement agent in connection with the Private Placement. If the Private Placement is consummated as discussed herein, the placement agent will receive aggregate fees of approximately $1,085,000 plus reimbursement for reasonable out-of-pocket fees and expenses.

Additional Information About the Consent Solicitation and Where to Find It

Stockholders of the Company and other investors are urged to read the consent solicitation that the Company will file with the Securities and Exchange Commission in connection with the Private Placement because it will contain important information about the Company, the Investors, the Private Placement, the persons soliciting proxies for the Private Placement and their interests in the Private Placement and related matters. Investors will be able to obtain all documents filed with the SEC by the Company free of charge at the SEC’s Internet site (http://www.sec.gov). In addition, documents filed with the SEC by the Company will be available free of charge from the Corporate Secretary of North American Scientific, Inc., 20200 Sunburst Street, Chatsworth, California, 91311, telephone (818) 734-8600. Read the consent solicitation carefully before making a decision concerning the Private Placement.

About North American Scientific

North American Scientific is a leader in radiation therapy in the fight against cancer. Its innovative products provide physicians with tools for the treatment of various types of cancers. They include Prosperaฎ brachytherapy seeds and SurTRAK™ needles and strands used primarily in the treatment of prostate cancer. In addition, the Company has been gaining clinical experience with its first generation ClearPath™ multi-channel catheter breast brachytherapy devices in 2007, and intends to launch the second generation devices in 2008. They are the only such devices approved for both high dose and continuous release, or low dose, radiation treatments. The devices are designed to provide flexible, precise dose conformance and an innovative delivery system that is intended to offer the more advanced form of brachytherapy for the treatment of breast cancer. Please visit www.nasmedical.com for more information.