Aspirin should be used to treat patients with acute myocardial infarction (MI) and continued indefinitely to reduce vascular death, nonfatal MI, and nonfatal stroke. Clopidogrel added to aspirin is beneficial in the treatment of patients with acute ST-elevation MI. Patients with unstable angina or non-ST-elevation MI should be treated with aspirin plus clopidogrel for at least 9 months to reduce the risk vascular death, nonfatal MI, and nonfatal stroke. Patients with prior MI should be treated indefinitely with aspirin and with clopidogrel if aspirin is contraindicated. Patients with ischemic stroke should be treated with either aspirin or clopidogrel indefinitely. Extended-release dipyridamole plus low-dose aspirin is more efficacious than low-dose aspirin but is associated with an insignificant increase in nonfatal MI and vascular death than low-dose aspirin. Clopidogrel is more effective than aspirin in reducing the risk of vascular death, nonfatal MI, and nonfatal stroke in patients with peripheral arterial disease.