The Primary Specific Aim of this randomized, multicenter clinical trial is to determine whether a 10 day course of treatment with clopidogrel 75 mg/day by mouth after a loading dose of 600 mg is as effective a similar treatment for 30 days in improving survival free from ischemic vascular events (ischemic stroke, myocardial infarction, and ischemic vascular death) at 90 days when subjects are randomized within 24 hours of time last known free of new ischemic symptoms in patients receiving aspirin 50-325 mg/day as the long-term antiplatelet therapy.