In an effort to evaluate the effectiveness of the Doppler Ophthalmic Test (DOT) following carotid endarterectomy, a large group of patients was examined both pre- and postoperatively with noninvasive techniques. The DOT, which has proven to be a useful non-invasive diagnostic test for the determination of significant carotid artery stenosis, was found to be persistently abnormal in 46% of patients with a preoperative positive test. This occurred in spite of the fact that operative arteriography, direct ultrasonic auscultation, and Doppler imaging studies were all within normal limits. It is suggested from this study that the Doppler Ophthalmic Test alone is not adequate to follow patients postoperatively, especially if an abnormal study persists following a satisfactory endarterectomy. Other non-invasive techniques, which employ direct ultrasonic imaging of the carotid flow, may be more accurate in determining vessel patency.