To determine the effect of surgical excision of pulmonary metastases from Wilms' tumor on postrelapse survival, we retrospectively analyzed the clinical courses of 211 patients with stages I to III, favorable or unfavorable histology Wilms' tumor entered on National Wilms' Tumor Study-1, -2, or -3 whose first recurrence was limited to the lungs. There was no difference in the 4-year postrelapse survival percentage of favorable-histology patients with a solitary pulmonary metastasis who did or did not undergo surgical removal of the metastasis in addition to pulmonary irradiation and chemotherapy. Although histological confirmation of pulmonary relapse is frequently indicated, the present data suggest that therapeutic removal of pulmonary metastases from patients with relapsed Wilms' tumor does not increase the percentage of patients who survive for 4 years postrelapse, compared with treatment with whole-lung irradiation and chemotherapy.