Platelets play a key role in the initial formation and progression of intravascular thrombus. During coronary and peripheral vascular interventions, antiplatelet therapy is used to impair platelet reactivity in order to minimize adverse ischemic events. Chronic antiplatelet therapy is also administered to decrease the long term risk of major adverse cardiovascular events in patients with high atherothrombotic burden. However, due to a heterogeneous response to antiplatelet agents, a substantial number of patients with cardiovascular disease remain at risk despite adherence to therapy. Since the availability of point-of-care rapid platelet function assays, quick and reproducible evaluation of platelet function after the administration of aspirin, thienopyridines, and glycoprotein IIb/IIIa inhibitors is possible. Various definitions of suboptimal platelet inhibition with oral antiplatelet therapy and associated risk factors are presented here. An algorithm to guide optimal antiplatelet therapy based on rapid platelet function testing during cardiovascular interventions is also presented.