Twenty eight patients with negative but technically satisfactory four-vessel angiography-admitted to our department from 1985 to 1995 were followed for long term evaluation. The aim of this retrospective study of patients with SAH of unknown etiology was to evaluate the clinical features, long-term prognosis in mortality rate and risk of rebleeding, and the daily functional capacity. Twenty eight out of 1035(2.7%) spontaneous subarachnoid hemorrhage patients were found to have subarachnoid hemorrhage(SAH) of unknown etiology. Twenty eight patients were confirmed as SAH, by computed tomography or lumbar puncture. CT scan was undertaken in all cases(in 28 cases within 5 days of hemorrhage). SAH of unknown etiology classified as Hunt and Hess grade I was 60.7% of cases, but there were no patients with Grade V. Arterial hypertension was present on admission in 35.7% of cases. We only performed the angiogram once in 16 of 28 patients, but there were no rebleedings caused by aneurysm. The period of follow-up ranged from 2 to 11 years, with the mean of 4.3 years. Only one of 28 patients(3.6%) experienced late rebleeding, and again had normal cerebral panangiography. Two patients(7.1%) showed a moderate disability in activities of daily living, one patient(3.6%) was mild disabled, and two(7.1%) had died of pneumonia. Based on the ADL grade, Grade I was 28.6% at the time of discharge however, during follow-up, increased up to 81.5%.