Children with bilateral Wilms tumor account for 5-7% of all patients with Wilms tumor. Certain patients, with syndromes associated with Wilms tumor development, have been identified to be at increased risk for bilateral tumors. Due to an increased risk for renal failure, patients with bilateral disease at presentation are treated with preoperative chemotherapy in order to preserve renal parenchyma. Although this recommendation was made nearly 30 years ago, patients with bilateral tumors have not been formally studied in prior cooperative trials. Recent evidence suggests that survival of these patients is inferior to similar patients with unilateral tumor. This study is designed to improve the survival of these children, while continuing the emphasis onpreserving renal function.