Nine hundred forty carotid endarterectomies were performed without the use of a temporary indwelling shunt. Six patients (0.6%) died, all from stroke; 17 other patients (1.8%) had another stroke, and 21 patients (2.2%) had temporary neurologic symptoms. Complete x-ray films detailing the opposite internal carotid artery and carotid artery back pressure were available for 783 operations. Correlation of stroke to back pressure, status of the contralateral internal carotid artery, preoperative neurologic deficit, and carotid clamp time was examined. Statistical analysis demonstrated significantly increased neurologic complications only if the systolic carotid back pressure was less than or equal to 50 mm Hg or the contralateral internal carotid artery was occluded. Analysis to determine if these factors were dependently related showed that when both a contralateral carotid occlusion and a carotid back pressure of less than or equal to 50 mm Hg coexisted (82 patients), the rate of permanent deficit was 11.0% compared with 2.8% when either factor was singly present and 0.9% when neither factor was present. No statistical difference exists between the group with only a single factor and those with neither factor. When a temporary shunt is not used during carotid endarterectomy, the risk of neurologic complication is increased if both a contralateral internal carotid artery occlusion and a carotid back pressure of less than or equal to 50 mm Hg coexist. The use of a shunt in this patient population may be beneficial.