The purpose of this study was to identify the prognostic significance of pulmonary and liver involvements present at diagnosis in children with Wilms' tumor. From 1971 to 2002, 57 patients with stage IV Wilms' tumor were diagnosed, treated, and followed in the authors' institution. Metastases were detected by chest radiography, abdominal ultrasonography, and/or thoracoabdominal computed tomography. Nephrectomy with tumor resection was performed and appropriate chemotherapy was given to all the patients. The Kaplan-Meier survival method was used to calculate survival. The log-rank test was used to compare the groups with respect to survival. The age range was 1.25 to 15 years (median 4 years). Thirty-seven patients had only lung metastases, 12 had only liver metastases, 6 had both lung and liver metastases, 1 had adrenal gland metastases, and 1 had other site metastases. The overall survival rate in the whole group was 37.1%. The overall survival rates for lung and liver metastases were 50.2% and 16.6%, respectively. The overall survival rates were significantly different between the two groups (P = 0.005). Only one patient survived in the group with liver involvement. Liver involvement at diagnosis indicates a worse prognosis than lung involvement. Wilms' tumor patients with liver metastases should be treated with more intensive regimens than those with lung metastases. Copyright © 2005 by Lippincott Williams & Wilkins.