The efficacy of radiation.MCNU (MR group) or radiation.MCNU.interferon-beta (IMR group) for malignant glioma was studied by a randomized trial at numerous medical facilities. MR group was irradiated with 50-60 Gy and intravenously injected with 2 mg/kg of MCNU on the initial day of irradiation and 6 weeks later. IMR group was also given intravenous administration of interferon-beta at the dose of 2 x 10(6) IU/m2 for 5 serial-days every eight weeks. There was no difference in background between the two groups. The response rate in MR group and IMR group was 44.4% (4/9) and 30.0% (3/10), respectively, showing no significant difference. The resected tumor volume before the start of these regimens seemed to correlate the response to the treatment in both groups. The major toxicity was myelosuppression, especially using MCNU with interferon-beta. These results indicated that this combined therapy is effective for malignant glioma, and should be executed further trials and follow up study.