Cardioembolic stroke represents a major healthcare challenge in the United States, accounting for significant morbidity and mortality, as well as economic and social costs. Determining the cause of ischemic stroke is often difficult because multiple potential etiologies are often present and available diagnostic tools are relatively insensitive. The diagnosis of cardioembolic stroke is based on a variety of clinical and laboratory clues that are significant, although not invariable, predictors of stroke etiology. Computed tomography scans help suggest etiology, and scans performed at 48 hours after stroke onset are essential to identify hemorrhagic infarctions. Cerebral angiograms may be helpful if performed early. Echocardiography is indicated only for selected patients who are more likely to demonstrate cardiac abnormalities on an echocardiogram. The management of acute cardioembolic stroke involves weighing the benefits of reducing stroke recurrence by anticoagulation against the risk of symptomatic brain hemorrhage. A management algorithm is provided that can help reduce both the risk of symptomatic brain hemorrhage and the incidence of potentially disabling stroke recurrence.