The clinical trial has become the standard method used to evaluate surgical procedures. Regarding carotid endarterectomy, clinical trials have reformed the indications for surgery as a means of decreasing the risk of stroke. The methodology and results from significant trials for the symptomatic and asymptomatic patient with carotid stenosis are described. Critical evaluation of these trials is necessary for the discerning surgeon to form a rational approach to clinical practice in carotid disease.