Recently, the benign nature of aneurysms of the cavernous carotid artery has been questioned. In a review of cases evaluated from 1980 to 1990 with this developmental aneurysm, the authors found 70 patients with 79 cavernous carotid artery aneurysms. As expected, the great majority (59 patients) had ophthalmoplegia as the initial problem. Retro-orbital pain (three cases) and a carotid-cavernous fistula (five cases) were infrequently the sole manifestation. Mirror-image asymptomatic aneurysms were found in nine patients and asymptomatic cavernous aneurysms were found in three additional patients. Thirty-four patients not surgically treated were followed for a mean of 2.8 years, and 36 surgical patients were followed for a mean of 4.1 years prior to treatment. Of the 79 aneurysms, one (1.3%) ruptured into the subarachnoid space during this period. Other than optic neuropathy or cranial neuropathy, no patient had a permanent neurological deficit; the 12 asymptomatic aneurysms remained asymptomatic. It is concluded that an aneurysm of the cavernous carotid artery is rarely associated with life-threatening complications, and treatment should be considered principally for patients with intolerable pain or problems related to vision.