A retrospective study was made of 195 patients who had ruptured intracranial aneurysms without significant intracerebral hematomas and who recovered to at least Grade III by Hunt and Hess' classification. The first 121 patients underwent aneurysm surgery 10 days to 2 weeks after subarachnoid hemorrhage (SAH) without repeat preoperative angiography and without special attention to volume replacement or avoidance of hypotension. Vasospasm resulted in cerebral ischemia in 15% of this group, more than half of these postoperatively, and was treated successfully in half the patients with a combination of aminophylline and isoproterenol. The later 74 patients were managed with aggressive maintenance of normal circulating blood volume and preoperative angiography at 2 weeks following SAH. If significant vasospasm persisted on angiography, surgery was delayed an additional week and, if spasm was still present then, aminophylline and isoproterenol was added prophylactically to aggressive volume replacement before surgery. In this second group of patients, the incidence of clinical vasospasm was essentially unchanged; however, it was almost completely limited to the preoperative period, and was more effectively treated with aminophylline and isoproterenol. Postoperative vasospasm was almost completely eliminated from the second group of patients.