Extensive experience has been accumulated with the use of preoperative therapy for children with Wilms' tumor. In selected cases, preoperative chemotherapy can reduce the morbidity of treatment. This is most appropriate for children with bilateral tumors in whom parenchymal sparing procedures are desirable. Patients with inoperable tumors and extensive intravascular tumor extension can also benefit from this approach. The NWTSG recommendations for preoperative chemotherapy in patients with Wilms' tumor are presented.