Between March, 1983, and February, 1989, 19 infants or children with chiasmal/hypothalamic gliomas were treated with chemotherapy after either surgical or radiological diagnosis. The patients ranged in age from 15 weeks to 15.6 years (median 3.2 years) at the start of therapy. Twelve patients were treated immediately after diagnosis because of progressive symptoms, and seven received chemotherapy after either radiographic progression or clinical deterioration, including progressive visual loss or intracranial hypertension. Based on biopsy results, seven of these tumors were classified as juvenile pilocytic astrocytomas, two as astrocytomas, two as highly anaplastic astrocytomas, and one as a subependymal giant-cell astrocytoma. There was associated neurofibromatosis in four patients. The two initial patients were treated with either actinomycin D and vincristine or 5-fluorouracil, hydroxyurea, and 6-thioguanine. The remaining patients received nitrosourea-based therapy; 15 evaluable patients were treated with a five-drug regimen that included 6-thioguanine, procarbazine, dibromodulcitol, 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU), and vincristine and one received 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU) and 5-fluorouracil. Fifteen of the 18 evaluable patients initially managed with chemotherapy either responded to therapy or their condition stabilized. Median time to tumor progression has not been reached at a median follow-up period of 79 weeks (range 6.6 to 303 weeks), and no tumor-related death has occurred with a median follow-up period of 79 weeks (range 18 to 322 weeks) from the initiation of therapy. The four patients who failed therapy or whose disease progressed after chemotherapy were treated satisfactorily with radiation therapy. Initial improvement or stabilization of visual function was obtained in 16 patients. Endocrine function remained stable in all patients during treatment, although three patients required pharmacological treatment for endocrinopathy that was present at diagnosis. These preliminary results suggest that nitrosourea-based cytotoxic regimens are useful for the initial treatment of children with chiasmal/hypothalamic gliomas, and allow potentially harmful radiation therapy to be deferred until progression of disease.