Renal neoplasms in the neonate are quite uncommon. Twentyseven of the 3,340 patients (0.8%) registered on the National Wilms' Tumor Studies from 1969 through April 1984, were 30 days old or less. Of these 27 patients, 18 had mesoblastic nephroma, 1 had a malignant rhabdoid tumor of the kidney, and 4 others had nonneoplastic lesions. The remaining four infants were reviewed in detail. All had favorable histology Wilms' tumors; none had distant metastasis at diagnosis. Treatment ranged from surgery alone to excision plus three-drug therapy for 15 months. All fared well. The patient with Stage I rhabdoid tumor died at eight weeks of age in spite of aggressive four-drug therapy. This review supports the view that Wilms' tumor in the neonate is extremely rare.