The purpose of this retrospective study was to determine the long-term prognosis of patients with asymptomatic pressure-significant (hemodynamically significant) internal carotid system lesions. Of 640 neurologically asymptomatic patients, 292 had pressure-significant internal carotid artery occlusive lesions as determined by ocular pneumoplethysmography, while 348 had a carotid bruit only without a pressure-significant lesion. The annual stroke rate for the first three years on a Kaplan-Meier life-table basis was 3.4% and 1.5% in the abnormal and normal ocular pneumoplethysmography groups, respectively, as compared with a rate of 0.5% in a normal age- and sex-matched population. The annual total event rate (transient ischemic attack and stroke) was 5.2% in the abnormal vs 2.3% in the normal group, with 56% of all events ipsilateral to the ocular pneumoplethysmography abnormality. These results indicate that patients with asymptomatic pressure-significant carotid system occlusive lesions are at greater risk for stroke than a normal ocular pneumoplethysmography group (twofold) and a general population (sevenfold).