From 1960 through 1981, 15 patients with cerebellar medulloblastoma, aged 16 years or over, were referred for irradiation following surgery. All patients received craniospinal irradiation; three patients received adjuvant chemotherapy. Five-year and 10-year survival rates of 63% and 38%, respectively, were obtained. The main cause of treatment failure was tumor recurrence in the posterior fossa. All local recurrences presented late, none developing within the first 3 years. One patient suffered systemic disease. The prognosis following relapse was poor. One patient achieved a prolonged remission following further surgery and radiotherapy, but died of treatment-related complications. The majority of the survivors are free of major deficit. One patient developed paraplegia 10 years after treatment. The possible risk of late damage to the hypothalamic-pituitary axis is discussed.