Carotid arteriography can be misleading in that roentgenographic occlusion of the internal carotid artery (ICA) may be suggested when the artery is actually anatomically patent. The distinction of occlusion versus pseudo-occlusion is crucial in recommending proper treatment. Aroused by the misinterpretation of two arteriograms by our radiology departments, a review of 780 arteriograms done on 780 patients during a three year period was begun. Of these, eight (1.0 per cent) symptomatic patients had conflicting arteriographic reports, with the radiologists reporting complete occlusion and the authors describing pseudo-occlusion. Established arteriographic criteria for pseudo-occlusion of the ICA are emphasized. These eight patients underwent carotid arterial exploration and all were found to have patent ICA. After successful carotid endarterectomy, seven of the eight patients have remained asymptomatic and have had no hemodynamically significant stenosis on noninvasive testing in the follow-up period, ranging from two to 38 months. Therefore, in evaluating patients with carotid territory symptoms, knowledge of the established arteriographic criteria for ICA pseudo-occlusion should alert the physician to the possibility of ICA patency. If this is suspected, the patient should undergo exploration of the carotid artery with subsequent endarterectomy if patency is demonstrated.