BACKGROUND: Platelets play a key role in many occlusive vascular disorders and anti-platelet agents are the most important therapeutic strategy in preventing the recurrence of cerebral infarction. In order to know the platelet aggregability according to the strategy of anti-platelet agents, we measured platelet aggregability in patients who were taking anti-platelet agents for cerebral infarction. METHODS: Platelet aggregability in response to adenosine diphosphate (ADP) or collagen was measured in whole blood samples from 175 patients (48 females and 137 males). It was analyzed according to the type of cerebral infarction, vascular risk factors, and each anti-platelet agent. RESULTS: Platelet aggregability induced by ADP or collagen was significantly increased in patients with large artery atherosclerotic infarction compared to those with small vessel disease. Among anti-platelet regimens, combined therapy with aspirin and clopidogrel decreased platelet aggregability most effectively. CONCLUSIONS: These findings suggest that anti-platelet treatment should be tailored to the vascular status of each patient, and that combination therapy with aspirin and clopidogrel can effectively modulate platelet aggregability in preventing the recurrence of cerebral infarction.