Abstract: We studied 139 cases were taking aspirin due to increased platelet aggregation.89 were males and 50 were females.They were divided into four groups(0,50mg,300mg,500mg,daily)with double-blind method.Platelet aggregation test was performed before and after taking aspirin.Clinical trials demonstrated that therels the benefit of aspirin in males and females.The most optimum dosage of aspirin is 50mg daily.

Key words: platelet aggregation, antithrombotic, critical dose