Forty children and adolescents showed clinical and radiographic evidence of brain stem tumors. The typical case is characterized by the insidious onset of cranial nerve involvement, pyramidal tract signs, ataxia, and behavioral changes without increased intracranial pressure. Of 28 patients who received radiation therapy, 21 (75%) showed clinical improvement. The average length of survival in the treated group was 47.2 months compared to 15.5 months in the untreated group. In general, patients who responded best to radiation therapy and survived longest were those with less extensive neurological involvement but longer duration of symptoms prior to diagnosis. In 26 pathologically verified cases, it appeared that the degree of tumor anaplasia was inversely related to survival time.