Extracranial to intracranial bypass surgery was used in 27 cases of intracranial giant aneurysm to prevent ischemic complications. In 19 of 21 patients the aneurysm was considered unfit for a direct clipping or ligation, and an EC-IC bypass was done in conjunction with staged clipping of the internal carotid artery or occlusion of the middle cerebral artery. All bypass grafts have remained patent postoperatively. None of the patients have developed ischemic complications in the 6--14 month period of follow-up.