This report documents, in seven infants younger than 2 years of age, a previously unrecognized association of a renal embryonal neoplasm (malignant rhabdoid tumor in six patients and a Wilms' tumor in one) with an embryonal primary tumor originating in the central nervous system. The neuroepithelial tumors included three cerebellar medulloblastomas, one pineoblastoma, one primitive neuroepithelial tumor (probably cerebral neuroblastoma), one malignant subependymal giant cell astrocytoma, and one cerebellar medulloepithelioma with divergent glial and neuronal differentiation. There is no evidence that this association is based on the selective neoplastic transformation of embryonal cells of similar histogenetic or cytogenetic origin. The relationship between these dissimilar, embryologically unrelated tumors remains enigmatic.