The diagnosis of transient ischemic attacks usually is based on an accurate history and physical examination (with the finding of carotid bruits), a complete neurologic examination, a brain scan, an encephalogram and an angiogram. Recently the Holter technique for continuous 24-hour electrocardiographic monitoring has been used as a diagnostic aid in these problem cases. Severe bradycardia, sick sinus syndrome, tachy-brady syndrome, recurrent tachycardia and heart block have been found to be the cause of the central-nervous-system symptoms in aged atherosclerotic patients. Correction with anti-arrhythmia drugs and pacemakers, with or without carotid endarterectomy, has been highly successful. Data are presented on 204 patients tested by Holter monitoring over a 2.5-year period in a small community hospital; 6 cases are illustrated in detail. The Holter monitor is a valuable tool in evaluating the patients with cerebrovascular insufficiency.