Cellular congenital mesoblastic nephroma is a potentially aggressive variant of the usually benign congenital mesoblastic nephroma. Our recent experience with 3 patients with cellular congenital mesoblastic nephroma prompted a critical review of the literature to evaluate risk factors for recurrence and present treatment programs. A total of 38 patients, including our 3 patients, with cellular congenital mesoblastic nephroma were divided into 2 groups: those with recurrent (7) and those with nonrecurrent (31) tumors. A statistical comparison of clinical and pathological data was performed. Of the 7 patients with local recurrence and/or pulmonary metastasis, 3 died. The average time to first recurrence was 5.4 months. Histological differences were not predictive of recurrent disease. Pathologically positive surgical margins (p less than or equal to 0.02) were the only statistically significant variable suggesting recurrent disease. While the presenting age was not predictive of recurrence (p equals 0.27), the relative risk of recurrence doubles in the first 3 months of life and quadruples after 6 months of life. Treatment programs also were evaluated. An infant with cellular congenital mesoblastic nephroma, regardless of age, is cured with surgery alone given clear pathological margins. In 4 of 5 children with recurrent tumors Wilms tumor treatment agents (vincristine and actinomycin D) failed to control local or distant disease. Of these cases 2 subsequently were treated with sarcomatous chemotherapy (vincristine, cyclophosphamide and doxorubicin) and both are in remission. These agents may prove to be more efficacious in the treatment of local or metastatic disease.