Thirteen patients with giant aneurysms of the internal carotid artery (ICA) were treated with ICA ligation and an extracranial-intracranial arterial bypass. A method for establishing a proper superficial temporal artery to middle cerebral artery pressure gradient while maintaining partial flow through the ICA is presented. This procedure allows the anastomosis to become established before full occlusion of the cervical ICA. None of these patients suffered any immediate or delayed ischemic or rebleed complications over an average follow-up period of 18 months.