Risk factors for stroke should be evaluated in patients who have had a transient ischemic attack. Blood pressure, lipid levels, and diabetes mellitus should be controlled. When applicable, smoking cessation and weight loss also are important. Angiotensin-converting enzyme inhibitor therapy may help prevent stroke. Aspirin is the treatment of choice for stroke prevention in patients who do not require anticoagulation. Clopidogrel is an alternative therapy in patients who do not tolerate aspirin. Atrial fibrillation, a known cardioembolic source (confirmed thrombus), or a highly suspected cardioembolic source (e.g., recent large myocardial infarction, dilated cardiomyopathy, mechanical valve, rheumatic mitral valve stenosis) are indications for anticoagulation.