This report is a retrospective analysis of 83 adults (greater than 16 years of age) with histologically proven or presumed primary neoplasms of the thalamus, hypothalamus, midbrain, pons, and medulla. Patients were treated with combined surgery and postoperative irradiation or with irradiation alone at the Washington University Medical Center (St. Louis, MO) from January 1950 through December 1984. Histologic analysis confirmed the diagnosis of tumor in 21, including nine with well-differentiated astrocytoma, four with astrocytoma with anaplasia, and eight with glioblastoma multiforme. Overall and disease-free survivals at 5 years were 28.7 and 23.2%, respectively. A statistical analysis was performed to ascertain the prognostic importance of the following variables: age, race, gender, duration of symptoms, cranial nerve paresis, primary site, extent of surgery, histology, and irradiation dose. The only factor identified by univariate analysis to be critical for survival was primary location of disease. Patients with supratentorial (thalamus/hypothalamus, midbrain) tumors had a 10-year disease-free survival of 15.4% compared to 29.6% for those with infratentorial (pons, medulla) tumors (P = 0.07). Patients with lesions of the pons had a 5-year disease-free survival of 35.8% compared to 13.8% for those with tumors of the thalamus (P = 0.05). Increasing irradiation dose was not correlated with superior survival. Factors evaluated but established to be insignificant were age (P = 0.27), race (P = 0.63), gender (P = 0.27), duration of symptoms (P = 0.19), cranial nerve paresis (P = 0.71), histologic type (P = 0.16), and extent of surgery (P = 0.94). Follow-up for 13 surviving patients ranged from 2.6 to 28.7 (mean, 12.0) years. Neurologic deficits in surviving patients were absent in 15% (two of 13), mild in 62% (eight of 23), and moderate in 23% (three of 13). One case of brain radionecrosis was identified (6000 cGy, 200 cGy daily).