A multi-center controlled double-blind clinical study was carried out to evaluate the effects of nizofenone in patients with subarachnoid hemorrhage who were treated within 2 weeks of the ictus. The test drug was administered as an addition to conventional therapy, which was maintained during the study. Of 208 patients studied, 102 were treated with nizofenone and 106 with placebo. Treatment with nizofenone was significantly more effective (p less than 0.05) than that with placebo based on functional recovery and other clinical findings. Although no significant difference was found in mortality rate between the nizofenone- and placebo-treated groups, a higher percentage of survivors in the former group exhibited a good outcome (p less than 0.05). The effects of nizofenone administration were found to be especially notable in patients with delayed ischemic symptoms, moderately severe preoperative deficits (Hunt and Hess Grade II or III), and diffuse high-density areas in pre- and postoperative computerized tomography scans. No significant side effects were observed.