ObjectivesDirect microsurgical clipping or endovascular coiling for complex and giant internal carotid artery (ICA) aneurysms is usually risky and leads to inadequate occlusion of the aneurysm. Extracranial–intracranial (EC-IC) bypass may help eliminate neurological complications. Materials and methodsWe retrospectively reviewed patients with intracranial aneurysms who were treated with the assistance of EC-IC bypass from July 2002 to February 2014. Six patients with complex ICA aneurysms were identified, and their clinical characteristics were analyzed. There were two men and four women ranging in age from 40 to 76 years. Three of these patients presented with hemorrhage, and two with compression with visual impairment. One aneurysm was an incidental finding during a physical examination. ResultsThree of the six ICA complex aneurysms were large or giant sized, one was an ICA blood blister-like aneurysm, one was a dissecting aneurysm, and one was a pseudoaneurysm due to tumor invasion. Bypass was performed with superficial temporal artery–middle cerebral artery anastomosis. The follow-up period ranged from 2 to 103 months (mean 36.67 months). The postoperative bypass patency rate was 100%. One patient had cerebellar intracerebral hemorrhage and one had temporary ptosis. There was no bypass surgery-related morbidity. The modified Rankin scale showed good outcomes in four of the six patients. ConclusionsCerebral revascularization plays an important role in the treatment of complex ICA aneurysms that have a significant mass effect on the optic nerve or require occlusion of the parent ICA as a salvage procedure.