The prevailing sentiment of North American neurosurgeons is that there is no significant difference in overall morbidity between patients who are treated with early aneurysm surgery and those who are treated with delayed aneurysm surgery. This concept is based primarily on the high incidence of ischemic events after early intervention. Recent experience, however, indicates that prophylactic hypervolemic hypertensive therapy may be beneficial in reducing delayed ischemia after early aneurysm surgery. During the preceding 21 months, we have performed 125 operations for intracranial aneurysms. Fifty-six patients in this group presented less than 7 days after subarachnoid hemorrhage (SAH) (47 within 3 days) and were treated by a prospective protocol of urgent aneurysm surgery performed within 24 hours after presentation. In all cases, the aneurysm was clipped with the use of mannitol and spinal drainage for brain relaxation. All patients were then treated with prophylactic volume expansion therapy and induced hypertension with a central venous pressure or a Swan-Ganz catheter until the 14th day after SAH. Preoperatively, 17 patients were Hunt and Hess Grade I, 9 were Grade II, 28 were Grade III, and 2 were Grade IV. In this group of 56 patients at risk for delayed ischemia from vasospasm, 5 patients had significant intraoperative complications. Ten patients (18%) had delayed cerebral ischemia, totally reversible in 6 cases, with small infarcts in 3 cases, and with 1 death (2% mortality from delayed ischemia), there were 5 cases of shunted hydrocephalus, and 3 deaths from other complications. Overall, 41 patients (73%) returned to their premorbid occupations without neurological deficit.(ABSTRACT TRUNCATED AT 250 WORDS)