Background: ACS remains a leading cause of death and disability. Platelet activation is a hallmark of ACS. Numerous lines of evidence suggest a mechanistic link between platelet hyper-function and myocardial damage in patients with ACS. Platelet GP IIb IIIa plays an important role in platelet aggregation and adhesion. Genetic polymorphism of that receptor was found to be associated with increase the risk of myocardial infarction and sudden cardiac death.Objectives: The aim of our study was to investigate the prevalence of various allelic forms of the PlA GPIIIa polymorphism in patients with ACS and whether it affects platelet reactivity.Methods: The present work constitutes a study on 40 patients presenting with ACS and 10 age and sex matched healthy volunteers, all subjects were genotyped using PCR-RFLP technique and their platelet reactivity was evaluated under high shear stress using Impact- R cone and plate-let analyzer device.Results: The PlA2 carriers were 47.5% in ACS patients compared to 20% in the control group. The distribution of PlA2 amongst patients with STEMI, NSTEMI and UA was 52.9%, 44.4% and 42.9% respectively. Also indices of platelet reactivity were higher in patients, especially those presenting with STEMI, than in healthy control and in carriers of PlA2 allele than in non carriers. However, these differences did not reach statistical significance probably due to small number of subjects included in the study.Conclusion: The prevalence PlA2 allele in the Egyptian population seems to be high compared to other ethnic groups, The role of PlA genetic polymorphism as genetic determinant of CHD and its effect on platelet reactivity need to be further evaluated in larger studies.