The effects of deliberate hypotensive anesthesia (DHA) on prognosis were analysed retrospectively in 112 patients who underwent early surgeries for ruptured cerebral aneurysms. Eighty-five patients received DHA (DHA group) and 27 patients were allocated to the control group. No difference was found in preoperative Hunt's grading, the time elapsed from subarachnoid hemorrhage to operation, arterial pressure before DHA. In the DHA group systolic arterial pressure was reduced to 80-90 mmHg for 87 +/- 6 min (M +/- SE) during operation. DHA had no effect on postoperative Glasgow Coma Scale, the incidence of post-operative complication, the period of hospitalization, and outcome (I: discharge with ability to walk, II: discharge with disability of walk, III: death). But DHA failed to reduce the incidence of intraoperative re-rupture, the prevention of which is the primary object of DHA. The mortality rate in the groups of Hunt's grade IV-V accompanied with the rate pressure product greater than 12,000 mmHg.min-1 was 55-80%. This suggests that in severely ill patients with ruptured cerebral aneurysm, the excitation of sympathetic efferents caused by the neural damage of hypothalamus might increase intracranial pressure and aggravate prognosis.