Acute ischemic stroke remains difficult to treat despite the advent of new therapies. The only approved medication to reverse its effects is recombinant tissue plasminogen activator administered intravenously within 3 hours of onset of stroke symptoms--an opportunity that does not often present itself. The principal drawback to thrombolytic therapy for acute ischemic stroke is a 3% to 6% occurrence of symptomatic cerebral hemorrhage. Although intra-arterial recombinant prourokinase also appears to be effective, it has not been approved by the Food and Drug Administration. Aspirin administered within 48 hours of stroke onset can prevent a few recurrent strokes and deaths. The efficacy of heparin and heparinoids in acute ischemic stroke has not been shown. Despite their theoretical attractiveness and laboratory results, neuroprotective agents have not proven effective in clinical trials. In view of current limitations on the ability to treat and reverse the effects of acute ischemic stroke, improved preventive measures in patients at risk for stroke are urgently needed.