A male patient, aged 42, (No. 780624) was admitted to the Department of Neurosurgery of Hirosaki University Hospital, complaining recent weight loss, intolerance to cold and visual disturbance of the right eye. Ophthalmological examination revealed the optic atrophy with decreased visual acuity and concentric visual defect of the right eye. Endocrinological examination showed almost general suppression of adenohypophyseal function except abnormal high level resetting of cortisol diurnal rhythm. Radiological examination revealed the accessory middle cerebral artery and giant internal carotid aneurysm of the right side which was displayed by contrast-enhanced CT scan, with the enlarged sella turcica. Good cross filling was seen in left CAG through the anterior communicating artery. Extra-intracranial end to end anastomosis of the right internal carotid artery was performed with long venous graft under general anesthesia with hypothermia and induced hypotension, on Oct. 26 '78. Unroofing of the right optic canal was very useful to preserve the optic nerve, and the body of the giant aneurysm was opened and sutured tightly to reduce its mass effect. Interlacing suture for the anastomosis of the cervical internal carotid artery was employed successfully. The blood flow of the bypass graft, measured as enough volume with square wave flowmeter during the operation, was also confirmed with postoperative angiography. After the episodes of gastrointestinal bleeding, hypotensive attack and hemorrhagic infarction of right frontal base, the postoperative final result was successful and the patient is doing well, 6 months after the operation.