Although tumors are a known complication of von Recklinghausen's neurofibromatosis (NF), they often develop after the second decade and their characteristics in the pediatric population are unclear. To define the frequency and distribution of tumor types in children with NF, the authors reviewed the experience at Children's Hospital of Pittsburgh between 1953 and 1984. During that time, 121 children younger than 18 years with documented NF were seen. Three patients (2.5%) developed locally extensive, unresectable sarcomas, two of which were clearly neural in origin. Two other children died from complications of highly cellular but not histologically malignant neurofibromas. Seventeen patients (14%) had brain tumors, of which 3 (2.5%) were malignant astrocytomas and 9 were optic gliomas. Two children had acute myelogenous leukemia. Although it has been said that patients with NF are particularly susceptible to the oncogenic effects of radiation, 12 children were treated with a median of 5000 rad to their tumor bed. Follow-up after radiation in that small cohort of patients ranged from 6 months to 12 years (mean, 6 years). Eleven of 12 patients experienced adequate local control. During the follow-up period, none developed a second tumor outside or within the radiation port that could be related to radiation. The authors conclude that clinically significant tumors in children with NF, not all of which are histologically malignant, are not rare. Although more prospective information is needed on response to and sequelae from therapy, the data in this report suggest no contraindication to aggressive therapy.