In a series of 404 patients with intracranial saccular aneurysm, 61 were over 65 years of age. Ten of these aged patients had no surgery. The operative mortality in the aged patients was 11.8%. While the mortality rate in patients below 65 years was 6.1%. The main complication following intracranial surgery for aneurysm consisted of cerebral infarction due to vasospasm, hydrocephalus, intracranial hematoma and general complications. The incidence of angiographical vasospasm was 22.6% in the aged patients and 43.6% in the young patients. There is no significant difference in vasospasm following subarachnoid hemorrhage between the aged and young patients. Cerebral infarction occurred in 27.5% of the aged patients and in 24.6% of the young patients. Severe cerebral infarction was found in 92.9% of the aged patients and in 58% of the young patients. Vasospasm resulted in broad cerebral infarction significantly more frequently in the aged patients, but cerebral infarction proved was non-fatal in the aged patients. Ventricular dilatation detected by CT was found in 33.3% of the aged patients and in 24.2% of the young patients. In patients with ventricular dilatation, 82.4% of the aged patients needed ventriculo-peritoneal shunt (V-P shunt). On the other hand, 39.3% of the young patients had V-P shunt. There was no significant difference for ventricular dilatation detected by CT between the aged and young patients. The aged patients depended on V-P shunt significantly more than did the young patients.(ABSTRACT TRUNCATED AT 250 WORDS)