IDIX (MM)

Idenix Pharmaceuticals, Inc. (Nasdaq:IDIX), announced today that Idenix management will participate in a panel discussion at Citigroup's 7th Annual Biotech Day on September 5, 2012 at 10:45 a.m. ET at the Mandarin Oriental, Boston, and present corporate overviews at the Stifel Nicolaus Healthcare Conference on September 6, 2012 at 3:15 p.m. ET at the Four Seasons, Boston and the Morgan Stanley Global Healthcare Conference on September 10, 2012 at 1:15 p.m. ET at the Grand Hyatt, New York City.

The live and archived webcasts of the company presentations can be accessed under "Events & Presentations" in the Idenix Investor Center at www.idenix.com. Please log in approximately 5-10 minutes before each event to ensure a timely connection. The archived replay will be available on the Idenix website for two weeks following the conferences.

About Idenix

Idenix Pharmaceuticals, Inc., headquartered in Cambridge, Massachusetts, is a biopharmaceutical company engaged in the discovery and development of drugs for the treatment of human viral diseases. Idenix's current focus is on the treatment of patients with chronic hepatitis C infection. For further information about Idenix, please refer to http://www.idenix.com.

CONTACT: Idenix Pharmaceuticals Contacts:
         Kelly Barry (617) 995-9033 (media)
         Daniella Beckman (617) 224-4471 (investors)