The ideal management of the patient with an asymptomatic stenosis of the extracranial internal carotid artery remains controversial. The purpose of this article was to evaluate the effects of prophylactic carotid endarterectomy (CE) done to treat asymptomatic carotid stenosis (greater than 50% diameter reduction by angiography) 10 years later. In 1976, 42 prophylactic CEs were performed. There were no postoperative deaths or strokes. During 10-year follow-up two strokes occurred in the operated hemisphere; one stroke was fatal and was due to an intracranial hemorrhage, whereas the other stroke was thromboembolic in origin. Two other patients suffered strokes in the contralateral hemisphere and seven patients had transient ischemic attacks in the contralateral hemisphere, which necessitated CE. The survival rate at the end of the study period by life-table analysis was 57% (mean 8.7 years). Sixteen late deaths occurred, with coronary artery-related disease the most common cause of death. This review with actual 10-year follow-up demonstrated that prophylactic CE may be performed with minimal risk, that late stroke in the operated hemisphere was negligible, and that long-term survival was similar to that of a comparable age-matched population, possibly because late deaths attributed to stroke were reduced. On the basis of long-term follow-up, CE to treat asymptomatic high-grade carotid stenoses appears to be indicated in appropriate patients.