Carmustine (BCNU) was employed as the only chemotherapeutic agent in a Radiation Therapy Oncology Group multimodality study comparing misonidazole-radiosensitized radiation therapy to conventional radiation therapy in 318 patients with malignant glioma. In 289 patients evaluable for BCNU pulmonary toxicity, there were no clinical manifestations of toxicity in patients receiving less than 902-mg/m2 total BCNU dose. Ten of 107 patients receiving more than this dose developed detectable pulmonary toxicity. Results of a multivariate regression analysis of risk factors, which corrects for survival time bias, suggested increased risk of pulmonary toxicity when total dose exceeds 1400 mg/m2. The risk of pulmonary toxicity was not increased by the administration of misonidazole and does not appear to be related to age.