Abstract Bilateral tumors were found in 33 patients or 5.4% of 606 children enrolled in the National Wilms' Tumor Study. Twenty six of 30 patients (87%) for whom detailed clinical information is available survived 2 yr after conservative surgery and radiation therapy. All patients were given one or more chemotherapeutic agents. A variety of surgical procedures were used including biopsy only, nephrectomy, and partial nephrectomies. Radiation therapy doses ranged widely, but between 1000 and 2000 rad apparently sufficed for local control in most cases. Recommendations regarding management by surgery, radiation therapy, and chemotherapy are given.