The authors reviewed the medical records of 94 patients who met the strict diagnostic criteria of spontaneous subarachnoid hemorrhage (SAH). They were diagnosed and treated at Seoul National University Hospital from January 1983 to June 1984. The interrelationships among the age, clinical status on admission, findings on brain computerized tomography (CT), site of the ruptured aneurysm and the intracranial complicaions (ventricular dilatation, vasospasm, rebleeding) and their outcome were studied. Conclusions obtained are as follows: 1) The local clot on CT (especially associated with ICH and /or IVH) was more frequently found in clinically poor patients than in good ones. 2) Cerebral angiography (TFCAs, 53 cases) revealed the anterior communicating artery (A-COM) to be the most common site of aneurysm in 21 cases (39.6%) and multiple aneurysms in 5 cases (9.4% : two in 4 cases, three in 1 case) and no aneurysm in 9 cases (17%). Vasospasm on angiography was found in 27 cases (50.9%). 3) Ventricular dilatation, which was measured on the first CT after SAH, was detected in 43 cases (45.7%). High incidence was found in the cases showing a local clot on CT (53.4%), especially associated with intraventricular hemorrhage (IVH; 83.3%), and in the cases of A-COM aneurysm rupture (52.4%; probably due to IVH). 4) The clinical vasospasm was edtected in 41 cases (43.6%). The interval between SAH and the development of clinical vasospasm ranged from from 3 to 35 days (mean 9.8 days). Thirty-five cases (85.4%) of them suffered from clinical vasospasm within 14 days. The incidence of clinical vasospasm steeply increased in the elderly patients (Fifties: 60%, Sixties: 66.7%) but that of findings of vasospasm on angiography (angiographic vasospasm) slowly increased with age. The local clot on CT seemed to be the most important factor of vasospasm, both clinically (51.7%) and angiographically (75%). The site of vasospasm on angiography was closely related with that of the ruptured aneurysm. 5) Rebleeding occurred in 21 cases (22.3%) with the interval ranging from 2 hours to 38 days (mean 10.1 days) after SAH and 14 cases (66.7%) of them rebled within 10 days. The shorter the interval after SAH, the higher the incidence. There were no definitely related factors affecting the rebleeding but it seemed to be affected to some extent by ICH and/or IVH on CT (31.3%). 6) Thirty-five cases (37.2%) diedof various causes. Mortality seemed to be most closely related with the clinical status on admission. Other related iactros were the aging, the local clot on CT (53.4%), especially associated with ICH and/or IVH (69.7%), and the development of various systemic or intracranial complications. Mortality seemed to be more closely related with ventricuar dilstation and rebleeding than with vasospasm. But it was suggested that vasospasm should be regrarded as a major cause of disabilities and an indirect cause of death.