More than 25 years after introducing preoperative chemotherapy for Wilms' tumor, the benefits of this approach are well known. The preoperative protocol results in easier operations with significantly fewer tumor ruptures during surgery and a favorable stage distribution. Acute toxicity and late effects are minimized without jeopardizing disease-free and overall survival. Future clinical trials of Wilms' tumor should seek additional risk factors to stratify and individualize treatment. These prognostic factors will improve the cure rates for high-risk patients by intensifying therapy and the quality of life for children with more favorable prognosis by lowering therapy to a minimum. As is true for radical surgery, partial nephrectomy in unilateral disease must be evaluated in carefully selected patients according to clear and well-defined indications. Molecular genetic studies should increase understanding of Wilms' tumor, influencing treatment and outcome.