Cerebrovascular disease is a major cause of morbidity and mortality. Approximately 75% to 80% of strokes and transient ischemic attacks are due to vascular disease within the cartoid or cerebral circulation. Of the remaining 20% to 25%, perhaps 50% are due to a cardioembolic event. Transesophageal echocardiography is the best screening test available for an unexplained cerebrovascular event. Anticoagulation with warfarin is indicated in the majority of cases of cardioembolic emboli. Atrial fibrillation is a major risk factor for stroke and prophylactic anticoagulation is warranted.