In a retrospective study of 44 patients with verified ruptured intracranial aneurysms, the results of radionuclide cerebral perfusion scintigraphy (dynamic brain scanning) and the presence or absence of arteriographic spasm were correlated with the clinical outcome. The data indicated that patients with normal dynamic scans had a better outcome as a group and following intracranial surgery than those in whom perfusion was reduced. Patients with normal perfusion had a higher incidence of preoperative rebleeding from their aneurysms, while patients with reduced perfusion had a higher incidence of infarction, especially after intracranial surgery. There was no correlation between the presence or absence of arteriographic spasm and the results of the dynamic scans, and nor correlation between the presence of absence of spasm and the outcome of the group as a whole. However, in some individual cases with severe spasm, reduced perfusion on the dynamic scan and a poor outcome were noted. It was concluded that the results of the dynamic scan correlated better with eventual patient outcome than the presence or absence of arteriographic spasm. It is therefore suggested that patients in Grades I and II with normal dynamic scans be operated on promptly to prevent rebleeding, and that surgery in patients in Grades I and II with abnormal dynamic scans be delayed until the dynamic scan returns to normal.