&NA;Ligation of the cervical internal carotid artery resulted in an acute neurological deficit in the dominant hemisphere of a 35‐year‐old man who suffered a penetrating injury to the neck. Regional cerebral hypoperfusion was suspected because the ischemic symptoms occurred while the patient was fully heparinized. Immediate institution of a barbiturate coma, volume expansion, and placement of a high‐flow extracranial‐intracranial arterial bypass graft led to rapid recovery of hemispheric function. High‐flow extracranial‐intracranial bypass grafts appear to be indicated for the treatment of symptomatic cerebral ischemia in selected cases of acute ligation or occlusion of the extracranial carotid artery. (Neurosurgery25:90‐92, 1989)