Item 8.01. Other Events.
On May 18, 2009, Henry L. Nordhoff, Chairman and former Chief Executive Officer ("CEO") of Gen-Probe Incorporated (the "Company"), established a stock trading plan pursuant to Rule 10b5-1 of the Securities Exchange Act of 1934 (the "Plan"), following his retirement as CEO of the Company on May 17, 2009. Mr. Nordhoff must exercise all outstanding stock options issued to him prior to February 7, 2007 on or before May 17, 2010 (the first anniversary of his retirement as CEO) or all such stock options will expire in accordance with the terms of the applicable stock option agreements.
Under the Plan, Mr. Nordhoff may exercise outstanding options to acquire up to an aggregate of 272,224 shares of Company common stock and sell the underlying shares. The Company believes that this amount represents approximately 27% of the aggregate Company stock and options to acquire Company stock held by Mr. Nordhoff as of the date of the Plan's adoption. The foregoing percentage includes all outstanding vested and unvested stock options and vested and unvested shares of Company stock underlying deferred issuance restricted stock awards held by Mr. Nordhoff as of the adoption of the Plan. The exercise of outstanding options owned by Mr. Nordhoff and the sale of underlying shares pursuant to the Plan are scheduled to occur in varying amounts between May 19, 2009 and October 30, 2009 depending on the available per share price. Any transactions occurring under the Plan will be disclosed publicly through Form 4 filings with the Securities and Exchange Commission and will be subject to the restrictions and filing requirements of Rule 144 of the Securities Act of 1933. Mr. Nordhoff may terminate the Plan at any time, subject to applicable securities laws.

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