Angiography has taught us much about the symptomatology of occlusion of the internal carotid artery; it may produce no symptoms or may be followed by variable complications. Simple occlusion may produce no sequelae if the circle of Willis functions efficiently and if adequate collateral circulation is established. If the individual is a child or young adult, ligation of the artery usually produces no untoward effect. Progressive obliteration of the lumen by atheroma often causes recurrent transitory disturbances due to localized cortical ischemia, e.g., aphasia, confusion or contralateral paresthesia or weakness. There may also be transitory amblyopia in the ipsilateral eye.