Cancer incidence is low in children. Childhood tumors are different from cancers seen in adults: their growth is rapid, but they respond well to radiotherapy and chemotherapy. In the case of Wilms Tumor, Actinomycin D, Vincristine and Doxorubicin were first used with success. Ifosfamide, Etoposide and Carboplatin are now also used in selected cases. But efficient treatments have important drawbacks: growth defects in the case of radiotherapy, late cardiac toxicity due to Doxorubicin, leukemias as second tumors following Etoposide. Treatment strategy is based on prognostic factors in Wilms' tumor, and the risk/benefit ratio assessment for each group of patients, considering survival probability and the risk of late effects. Large randomised studies in the USA and in Europe resulted in cure rates over 90%, with very few expected sequelae. Preoperative chemotherapy is now successfully applied to other tumors in children.