Platelets play a dominant pathogenic role in the development and outcome of acute coronary syndrome(ACS). This syndrome including (unstable angina, ST-elevation myocardial infarction and non ST-elevation myocardial infarction). Aspirin therapy in combination with clopidogrel is today still the recommended platelet inhibitory treatment regimen for management of high risk patients presenting with (ACS).Platelet aggregation is tested in the presence adenosine 5- di phosphate (ADP) using platelet aggregometer. The present study was done to evaluate the anti platele response of clopoidogrel in patients with (ACS). Our study revealed statistically significant difference between control and study group as regard to platelet aggregation levels . The mean of platelet aggregation among diabetics was higher than non-diabetic in both groups. The results supported that dual antiplatelet therapy (aspirin plus clopidogrel) in acute coronary syndrome had a potent effect on platelet aggregation without significant increase in the risk of bleeding.