Perioperative complications were increased in the presence of certain risk factors, an occlusion of the nonoperated-on (contralateral) carotid artery, a thrombus visible on the angiogram of the symptomatic lesion, the presence of a computed tomographic image showing a lesion compatible with ischemia in the area of the brain supplied by the diseased artery, a history of diabetes, a diastolic blood pressure higher than 90 mm Hg, an irregular or ulcerated plaque visible on the angiogram, and, surprisingly, a lesion on the left side rather than the right side. This unexpected phenomenon would have been dismissed were it not for the fact that it has been observed in 2 other contemporary carotid endarterectomy databases.15,16 In the NASCET, a survey was made of the handedness of the surgeons. The left-handed surgeons did not experience the doubling of complications when operating on the left side that was observed for the surgeons who were right handed. When performing endarterectomy on the right side, the left-handed surgeons had a complication rate similar to that of right-handed surgeons (NASCET, unpublished data, 1998). These risk factors lead to a doubling or slightly greater immediate operative risk. All factors that individually increased the perioperative risk, except for the presence of an intraluminal thrombus, were followed by ultimate benefit as evidenced by improved stroke-free survival at 5 years compared with patients treated only with the best medical care.