Backgound: Thrombosis is regarded to be a key factor in the development of acute coronary syndromes in patients with coronary artery disease (CAD), Platelets are known to play a fundamental role in acute coronary syndromes(ACS). After atherosclerotic plaque rupture, platelets can form pathogenic, occlusive thrombi leading to acute ischemic events. The precise mechanisms of platelet activation in acute coronary syndromes are still under investigation. Physical activity could regulate the development of ACS via effects on platelet function. Several studies have shown that acute physical exercise increases platelet reactivity, typically assessed by aggregation assays, in both healthy individuals and in patients with cardiovascular disease. The aim of this study  was to investigated the effect of moderate and strenuous exercise on arterial thrombus formation.   Subjects and Methods: Assay of some hemostatic marker as Platelet activation  , thrombin generation (TF(pg/ml),TAT_ µ g/l and dimerand  tPA  concentration ) von Willebrand factor,platelet aggregation tests,Coronary Angiography. haemostatic parameters in patients with ACS correlated with other  clinical  parameters under  physical exercise .   Results: Patients with ACS showed higher values for fibrinogen , tPA ,   TAT_   , as indicators for a thrombin synthesis, and a marker for prothrombotic conditions, was elevated in patients with ACS,. Von Willebrand factor and D-dimer showed no statistical significant differences during rest., Exercise increased hemostatic parameters in an strenuous physical exercise in ACS Patients( < 0.05).  Exercise also increased plasma levels of fibrinogen and von Willebrand factor ,but there was an increase in the generation of T-AT complexes,. (P < 0.05). Exercise did not affect platelet aggregation regardless of its intensity when triggered by the agonists ADP or collagen.   Conclusion: Strenuous but not moderate exercise increases the thrombotic tendency in healthy sedentary male volunteers     .