One hundred twenty-nine consecutive carotid endarterectomies performed for atherosclerotic ulcerative stenosis without the use of intraoperative shunting were analyzed prospectively in an effort to determine the significance of intraoperative ischemia. Intraoperative EEG and regional cerebral blood flow measurements were used to monitor these patients. Ten of the patients were excluded because of inadequate data, but none of these 10 patients experienced a complication. Factors analyzed included preoperative risk assessment according to the Mayo Clinic system of Sundt et al., intraoperative regional cerebral blood flow measurements, and intraoperative EEG changes. The overall mortality rate was 2.5%, the major morbidity rate was 2.5%, the minor morbidity rate was 1.7%, and the rate of transient neurologic dysfunction was 1.7%. The patients' preoperative state as determined according to the Mayo Clinic system of Sundt et al. was more useful in identifying patients at risk than was intraoperative EEG and regional cerebral blood flow monitoring.