A patient with a rapidly enlarging symptomatic false aneurysm of the internal carotid artery 30 years after nonoperative treatment of a penetrating neck injury is presented. Preoperative compression of the aneurysm precipitated transient cerebral ischemic attacks. Complete interruption of the right internal carotid artery inflow during aneurysmectomy was considered to be fraught with great danger. An extra-intracranial arterial bypass was therefore performed, and then aneurysmorrhaphy was easily performed and saphenous vein graft interposition accomplished. The importance of early definitive treatment of arterial injuries is emphasized. The bypass used allowed additional cerebral blood flow when complete occlusion of the carotid artery was contraindicated.