Cystic partially differentiated nephroblastoma is a relatively rare tumour of the kidney usually affecting infants. Cystic Wilms' tumour and multilocular cystic nephroma should be distinguished from cystic partially differentiated nephroblastoma. Multilocular cystic nephroma is a benign tumour whereas cystic Wilms' tumour is at the malignant end of the range of classification of such tumours. Cystic partially differentiated nephroblastoma may undergo local recurrence but there is no report of metastasis.