624 patients with acute ischemic stroke treated within 90 minutes (302 patients) or 180 minutes (322 patients) from stroke onset with defined time of onset, measurable deficit on National Institutes of Health stroke scale (NIHSS), and computed tomographic (CT) scan of the brain without evidence of intracranial hemorrhage. Average age was 66 to 69 years, and median NIHSS score was 14 to 15 in each group. Exclusion criteria included no stroke in preceding 3 months, major surgery within 14 days, systolic blood pressure >185 mm Hg, rapidly improving symptoms, or gastrointestinal hemorrhage within previous 21 days.