Thirty-six proven cases of medulloblastoma were reviewed by serial CT follow-up examinations from 4 months to 10 years, 2 months after the initial diagnosis, with a mean follow-up time of 3 years, 9 months. The children ranged in age from 10 months to 16 years, 7 months at the time of follow-up. The tumor recurred at the primary site in 20 cases (56%). Leptomeningeal metastasis was demonstrated on CT in 14 cases (39%); seven of these patients also presented with solid subarachnoid metastases. Thirteen patients (36%) showed evidence of severe brain atrophy, which was confined to the posterior fossa in seven of the 13. Calcification resulting from mineralizing microangiopathy developed in five cases (14%), including three patients who had extensive dystrophic calcification in the corticomedullary junction and the deep-seated nuclei of the cerebrum and cerebellum. Only one case of leukoencephalopathy was observed. The patterns of tumor recurrence in the posterior fossa that is severely deformed by surgery and other treatment modalities and leptomeningeal spread of tumor are discussed.