Cerebral arterial spasm following subarachnoid hemorrhage can be responsible for secondary neurological deficits and can influence history, prognosis, and results of surgical treatment. The demonstration of vasospasm can be important for therapy. The use of I-123 HIPDM and SPECT in evaluating regional cerebral blood flow showed the effects on cerebral perfusion of diffuse arterial spasm in a case of subarachnoid hemorrhage and its recovery. There was a parallel with clinical neurological status.