Platelets play a critical role in formation of coronary thrombosis. An enhanced systemic platelet activation plays a significant role in the acute coronary syndrome. Despite better interventional techniques and better concomitant pharmacological therapy, the degree of platelet activation contributes significantly to prognosis and postinterventional event rate. Residual platelet activation after intervention is often associated with an enhanced initial platelet activation prior interventional treatment. An effective antiplatelet therapy is of utmost importance for the acute therapy and for secondary prevention in patients undergoing coronary interventions or with acute coronary syndrome. The efficacy of the antithrombotic therapy determines the long term prognosis in these patients.