To the Editor.
—I read with interest the Asymptomatic Carotid Atherosclerosis Study (ACAS)1 regarding carotid endarterectomy in asymptomatic patients, primarily because I am a surgeon who frequently performs this operation. The results of the North American Symptomatic Carotid Endarterectomy Trial (NASCET)2 were quite impressive in confirming the benefits of carotid endarterectomy in symptomatic patients with high-grade stenoses. The finding that the percentage of major ipsilateral stroke in medical patients was 13.1% compared with 2.5% in surgical patients was particularly compelling. Unfortunately, although the ACAS was well designed, my interpretation of the data is far different than the reported conclusions and confirms convincingly that there is little or no benefit from carotid endarterectomy in asymptomatic patients. I have several concerns.First, only observed data (mean follow-up of 2.7 years) are acceptable. Extrapolation to 5 years to find statistical significance is not justified when no benefit was observed beyond 2.5