CAMBRIDGE, Mass.–Helicos BioSciences Corporation (Nasdaq: HLCS – News) announced today that it has priced its initial public offering of 5,400,000 shares of common stock at $9.00 per share. All of the common stock is being offered by the company, and the common stock will trade on the NASDAQ Global Market under the symbol “HLCS.” The company has granted the underwriters an option to purchase up to an additional 810,000 shares to cover over-allotments, if any.

UBS Investment Bank is acting as the sole book-running manager for the offering. J.P. Morgan Securities Inc. is acting as a joint lead manager, with Leerink Swann & Company and Pacific Growth Equities, LLC acting as co-managers.

A registration statement was declared effective by the Securities and Exchange Commission on May 24, 2007. This release shall not constitute an offer to sell or the solicitation of an offer to buy, nor shall there be any sale of these securities in any state or jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such state or jurisdiction.

Copies of the final prospectus relating to the offering may be obtained from the prospectus department of UBS Investment Bank, Attn: Prospectus Department, 299 Park Avenue, New York, NY 10171 (212-821-3000).

About Helicos BioSciences

Helicos BioSciences Corporation is a life sciences company developing innovative genetic analysis technologies for the research, drug discovery and clinical diagnostics markets. The company has developed its proprietary True Single Molecule Sequencing technology to enable ultra-high-throughput genetic analysis based on the direct sequencing of single molecules of DNA or single DNA copies of RNA. The company’s corporate headquarters are located at One Kendall Square, Building 700, Cambridge, MA 02139, and its telephone number is (617) 264-1800.

Contact:

Helicos Biosciences

Louise Mawhinney, 617-264-1870