A survey was conducted by the Radiation Oncology Discipline Committee of the Pediatric Oncology Group to provide an estimate of the outcome of treatment with modern radiotherapy of brain stem tumors in children. Thirteen of thirty-eight institutions submitted data for 62 patients who had been diagnosed between 1972 and 1981, who had completed planned treatment with radiotherapy, and for whom follow-up information was available. The results were poor. Fourteen patients were alive with no evidence of recurrence between 11 and 154 (median 50.5) months post-treatment, two were alive with disease at 22 and 24 months, and forty-six died of disease at intervals ranging from 2 to 30 (median 8.7) months from initiation of treatment. Actuarial survival was 50% at 1 year, 29% at 2 years, and 23% at 5 years. The age of the patient, the surgical approach, and the volume and dose of radiotherapy all appeared to correlate with outcome on univariate analysis; but on multivariate analysis a statistically significant survival advantage was found only for patients greater than 5 years of age who had undergone surgery as part of their treatment. Possible explanations for these findings are discussed, and the roles of surgery, radiotherapy, and chemotherapy are reviewed.