Extracranial-intracranial arterial bypass was performed for intracranial internal carotid artery stenosis in 105 patients who had ischemic symptoms 1 to 3 months before operation. The degree of stenosis, measured angiographically, was 60 to 98%. The postoperative bypass patency rate, determined angiographically or by Doppler examination, was 97%. The surgical mortality rate was 1%, and the permanent surgical morbidity rate was 2%. During a mean follow-up period of 54 months, 22 patients died; 10 deaths were caused by cardiac disease and 3 were related to stroke, 2 of which were ipsilateral to the bypass. One patient was lost to follow-up. Seventy-three of the 82 survivors (89%) had no further transient ischemic attacks or stroke after operation. Seven patients had a late stroke: 5 were ipsilateral, 1 was contralateral, and 1 was vertebrobasilar. Three of these strokes were fatal. The overall late death rate was 4% per year, and the late death rate from neurological causes was 0.6% per year. The late stroke rate was 1.5% per year, and the rate of ipsilateral late stroke in patients who had a patent bypass was 0.6% per year. We conclude that extracranial-intracranial arterial bypass for symptomatic intracranial internal carotid artery stenosis is a reasonably safe and technically satisfactory procedure that has a potential for improving outcome, compared with the natural history of the disease.