This report documents the occurrence of an extrarenal nephroblastoma from which a cerebellar metastasis developed in a four-year-old girl with spina bifida. The second tumor became symptomatic two years after the resection of the primary, suggesting a treatment effect as a factor for the delay in the growing of the metastatic neoplasm. Histologic and ultrastructural features of the metastasis were similar to those described in Wilms' tumors of the kidney. The pathogenesis of this exceptional association, including malformation, malignancy, and unusual site of metastasis, is discussed.