Stroke is the most common cause of adult mortality in the United States. Antithrombotic agents form the mainstay of stroke prevention. Aspirin produces a modest reduction in the risk of second stroke and transient ischemic attack (TIA, mini-stroke) and is widely recommended for initial therapy. The thienopyridines (Ticlid) and clopodogrel (Plavix) are alternatives for secondary prevention in patients who do not respond to or cannot take aspirin. They...