Roche, a world-leading healthcare provider of pharmaceuticals and diagnostics, has extended its offer to acquire all of the outstanding common shares of Ventana Medical Systems, Inc. to 5:00 p.m., New York City time on Thursday, September 20, 2007.

According to a Roche press release the tender offer was previously scheduled to expire at 5:00 p.m., New York City time, on August 23, 2007. All other terms and conditions of the tender offer remain unchanged. As of the close of business on August 21, 2007, approximately 13,430 shares have been tendered pursuant to the offer.

On June 27, 2007, Roche commenced a tender offer to acquire all of the outstanding common shares of Ventana for $75.00 per share in cash. This price represents a 44 per cent premium to Ventana's close of $51.95 on June 22, 2007 (the last trading day prior to the announcement of Roche's offer) and a 55 per cent premium to its three-month average as of the same date of $48.30.

Greenhill & Co. and Citi are acting as financial advisors to Roche and Davis Polk & Wardwell is acting as legal counsel.