Seven patients with symptomatic aneurysms involving the petrous segment of the internal carotid artery were treated by endovascular techniques (six patients) or surgical ligation (one patient). Patients' ages at the time of treatment ranged from 7 to 62 years (mean, 30 years). The presenting symptoms were pain (seven patients), eighth nerve dysfunction (three patients), seventh nerve dysfunction (one patient), fifth nerve dysfunction (two patients), and bruit (one patient). Two patients, ages 7 and 19, respectively, presented with giant, partially thrombosed petrous aneurysms and had hemiatrophy of the body ipsilateral to the side of the aneurysm. Only one patient had a history of trauma; aneurysms in the remaining patients were presumed to be congenital in origin. In one patient with a saccular aneurysm, a balloon could be navigated into the aneurysm, obliterating it but preserving the parent artery. The remaining six patients had fusiform aneurysms with intraluminal thrombus and underwent proximal occlusion (four patients) or trapping procedure (two patients). In all patients, symptoms were alleviated after thrombosis of the aneurysm. The only complication was a transient visual loss in a hypercoagulable patient, occurring after carotid occlusion. Petrous carotid aneurysms can produce a wide clinical spectrum of signs and symptoms in younger patients; these aneurysms frequently are fusiform and contain chronic thrombus. They can be treated effectively by endovascular or surgical occlusive procedures.