BACKGROUND: Patients with stenos4is of one carotid artery and occlusion of the contralateral carotid artery (stenosis-occlusion) who are treated medically am at high risk for stroke. We have recently reported that carotid endarterectomy on the stenotic artery has a low perioperative risk in these patients, We now present follow-up data to define the long-term effectiveness of this operation. PATIENTs AND METHODS: From 1985 to 1991, 135 patients with stenosis-occlusion underwent endarterectomy of the stenotic carotid artery: Selective intra-arterial shunting was performed based on mental status changes under regional anesthesia, preoperative neurologic deficit, or evidence of preoperative cerebral infarction on computed tomography scan. Shunting was used in 70 patients (52%), Saphenous vein was used for parch closure in 132 patients (98%), and polytetrafluroethylene in 3 (2%). RESULTS: By life-table analysis, 92% of patients have remained stroke-free at 5 years. Fourteen deaths, none related to cerebrovascular disease, have occurred during follow-up. The life-table cumulative Stroke-free survival rate at 5 years is 74%, and the overall survival rate is 82%. CONCLUSION: Carotid endarterectomy in the presence of a contralateral occlusion provides long-term benefit to the patient with respect to prevention of stroke. With lower perioperative stroke rates and proven long-term benefit, carotid endarterectomy of the stenotic artery should be the treatment of choice in the patient with stenosis-occlusion.