SINCE the introduction of carotid arteriography, many unsuspected cases of occlusion of the internal carotid artery have been discovered. In the last 13 years approximately 45 cases have been reported, the diagnosis resting to a great extent on roentgenologic evidence. Recent clinical and pathological studies have led me to the conclusion that thrombosis of the internal carotid artery is much more frequent than these figures indicate. Indeed, it may well prove to be one of the major causes of apoplexy. This impression is confirmed by Hultquist,1who, in his extremely thorough study of the pathological aspects of this subject, found thromboembolism of the carotid system in about 3 per cent of routine autopsies. Clinicians and pathologists have heretofore failed to appreciate this condition, because the cervical portion of the carotid artery lies in a "no-man's land" between general pathology and neuropathology, its examination at autopsy being therefore neglected. Chiari,