Several randomized clinical trials (RCTs) were performed to compare carotid endarterectomy (CEA) and drug therapy for the treatment of significant carotid stenosis. CEA was recommended for symptomatic patients with significant carotid stenosis if the risks of postoperative stroke and death were less than 6%. In asymptomatic patients, immediate CEA halved the net 5-year stroke risk, resulting in long-term benefits if the risks of postoperative stroke and death were less than 3%. The annual risk reduction was 1% in asymptomatic patients. RCTs conducted to compare treatment with aspirin and new antiplatelet drugs concluded that a risk reduction was achieved in patients who received new antiplatelet drugs.