Thrombus formation is a crucial event in acute coronary syndromes, bypass occlusion, and stent thrombosis. In the coronary circulation, platelet activation is an initial event,while expression of tissue factor and subsequent activation of the coagulation cascade and invading white blood cells solidify the evolving clot, an event that often leads to vascular occlusion. Platelets are primarily activated by thromboxane and ADP via thromboxane and P2Y12 receptors on the platelet surface that eventually lead to the expression of the glycoprotein IIB/IIIA receptor that binds fibrin. Twenty-one years ago, the first randomized clinical trial established the superiority of dual antiplatelet therapy over anticoagulant therapy among patients undergoing percutaneous coronary intervention. Thus, dual antiplatelet therapy has become a crucial therapeutic intervention in patients with stable or acute coronary artery disease.