We followed 40 patients with unilateral carotid occlusion by serial clinical and Doppler evaluation for over 6 years. Two groups were identified: 19 patients had already occluded their arteries on entry to the study, and 21 progressed to occlusion during the course of the study. No strokes occurred in the first group during follow-up, and the annual stroke rate in the second group was 3.8% for the territory of the occluded artery and 5.7% for all vascular territories. Death rate was 6.6% annually for both groups, mainly cardiac. Transcranial Doppler with digital compression of each carotid artery demonstrated middle cerebral artery (MCA) dependent on the patent carotid being total in 50% and partial in 30%. There was no correlation between degree of stenosis and MCA dependency (r = -0.24). Our data on stroke risk in asymptomatic patients with unilateral carotid artery occlusion indicate a benign outcome.