BACKGROUND Carotid endarterectomy (CEA) is associated with a risk of cerebral ischemia during carotid clamping, hence various cerebral protection strategies, including pharmacological management and routine or selective shunting, are commonly available. This study aimed to analyze the results of CEA with intraoperative electroencephalographic (EEG) monitoring to identify factors associated with EEG changes consistent with cerebral ischemia which needed shunting. METHODS A prospectively compiled, computerized database of all primary CEAs performed at our institution with EEG monitoring for symptomatic or asymptomatic severe carotid lesions between January 1990 and June 2009 was analyzed. RESULTS In all, 1,914 CEA procedures were performed on 1,696 patients, of which 218 had staged bilateral CEAs. EEG changes were recorded in 392 patients (20.5%), but a shunt was inserted during 312 CEA procedures (16.3%). Multivariate analysis showed that a symptomatic presentation (odds ratio [OR], 1.37; 95% confidence intervals [CI], 1.07-1.76; p = 0.012), prior stroke (OR, 2.28; 95% CI, 1.66-3.13; p < 0.001), contralateral carotid occlusion (OR, 2.14; 95% CI, 1.18-3.91; p = 0.019), and moderate (<80%) ipsilateral carotid disease (OR, 1.95; 95% CI, 1.08-3.52; p = 0.033) predicted the need for shunting. CONCLUSIONS EEG was an excellent detector of cerebral ischemia and a valuable tool in guiding the need for shunting. Patients who were symptomatic or had a history of stroke, a contralateral carotid occlusion, or an ipsilateral moderate carotid stenosis were more prone to EEG changes consistent with cerebral ischemia. Surgeons should consider EEG changes during clamping as an effective criterion for selective shunting.