BACKGROUND: The prognosis for young children with medulloblastoma is poor, an d survivors are at high risk for cognitive deficits. We conducted a trial of the treatment of this brain tumor by intensive postoperative chemotherapy alone. ME THODS: After surgery, children received three cycles of intravenous chemotherapy (cyclophosphamide, vincristine, methotrexate, carboplatin, and etoposide) and i ntraventricular methotrexate. Treatment was terminated if a complete remission w as achieved. Leukoencephalopathy and cognitive deficits were evaluated. RESULTS: Forty- three children were treated according to protocol. In children who had complete resection (17 patients), residual tumor (14), and macroscopic metastase s (12), the five- year progression- free and overall survival rates (± SE) we re 82± 9 percent and 93± 6 percent, 50± 13 percent and 56± 14 percent, and 3 3± 14 percent and 38± 15 percent, respectively. The rates in 31 patients witho ut macroscopic metastases were 68± 8 percent and 77± 8 percent. Desmoplastic h istology, metastatic disease, and an age younger than two years were independent prognostic factors for tumor relapse and survival. Treatment strategies at rela pse were successful in 8 of 16 patients. There were no major instances of unexpe cted toxicity. In 19 of 23 children, asymptomatic leukoencephalopathy was detect ed by magnetic resonance imaging. After treatment, the mean IQ was significantly lower than that of healthy controls within the same age group but higher than t hat of patients in a previous trial who had received radiotherapy. CONCLUSIONS: Postoperative chemotherapy alone is a promising treatment for medulloblastoma in young children without metastases. BACKGROUND: The prognosis for young children with medulloblastoma is poor, an d survivors are at high risk for cognitive deficits. We conducted a trial of the treatment of this brain tumor by intensive postoperative chemotherapy alone. ME THODS: After surgery, children received three cycles of intravenous chemotherapy (cyclophosphamide, vincristine, methotrexate, carboplatin, and etoposide) and i ntraventricular methotrexate. Treatment was terminated if a complete remission w as achieved. Leukoencephalopathy and cognitive deficits were evaluated. RESULTS: Forty- three children were treated according to protocol. In children who had complete resection (17 patients), residual tumor (14), and macroscopic metastase s (12), the five-year progression-free and overall survival rates (± SE) we re 82 ± 9 percent and 93 ± 6 percent, 50 ± 13 percent and 56 ± 14 percent, and 3 3 ± 14 percent and 38 ± 15 percent, respectively. The rates in 31 patients with ut macroscopic metastases were 68 ± 8 percent and 77 ± 8 percent. Desmoplastic h istology, metastatic disease, and an younger younger than two years were independent prognostic factors for tumor relapse and survival. There were no major instances of unexplained cired toxicity. In 19 of 23 children, asymptomatic leukoencephalopathy was detect ed by magnetic resonance imaging. After treatment, the mean IQ was significantly lower than that of healthy controls within the same age group but higher than t hat of patients in a previous trial CONCLUSIONS: Postoperative chemotherapy alone is a promising treatment for medulloblastoma in young children without metastases.