Thirty-four infants under 1 year of age with Wilms' tumor were diagnosed and treated in 14 Italian pediatric oncology units during 1970-79. The 3-year survival rates decreased with higher group unilateral tumors: 95% in group I Wilms' tumor, 75% in group II and 20% in group III. The survival rates for children with group I and II Wilms' tumor were similar for those who were treated with surgery and chemotherapy and those who also received postoperative radiotherapy. During 1975-79 fewer patients with group I Wilms' tumor received radiotherapy (1 of 11) than during 1970-74 (4 of 6, p less than 0.05). All these children are alive at this writing.