Patients suffering subarachnoid hemorrhage in whom angiography does not initially show vascular malformation and CT scan rules out an intracranial tumor, have, reportedly, a good prognosis with a rate of recurrent hemorrhage of about 2-10% within a follow-up time of up to 15 years. Most authors denied indication for control angiography. In order to study the benefit of control angiography performed after 4-6 weeks, four-hundred eighty-three patients with SAH but without ICH were reveiwed, and the longterm clinical course of 98 patients with SAH of unknown origin treated in our department between 1976 and 1988 was investigated. Among 183 patients who underwent control angiography, a second angiography showed an aneurysm in 143. The third angiography was positive in a further 18 patients. Recurrent SAH occurred early only in patients who had undergone only one angiography. One patient died from intracerebral hemorrhage of unknown origin two years following SAH. These data support the need for control angiography in cases of SAH.