The case of a 16-month-old female infant with bilateral cystic nephroblastomas, Dandy-Walker syndrome, microcephaly, bilateral cataracts, and cerebellar heterotopia is reported. The patient's older sister, who had had bilateral cystic nephroblastomas, botryoid sarcoma involving the vagina and urinary bladder, microcephaly, arhinencephaly, and bilateral cataracts, was described in a previous report. Chromosomal study in the present case confirmed trisomy 8 mosaicism (rate of mosaicism, 16 per cent). The familial occurrence and the chromosomal disorder suggest a syndrome involving genetic abnormalities.