Treatment of Wilms' tumor is an example of success of modern oncology. A combination of surgery, radiotherapy, and chemotherapy is widely accepted as the efficacious treatment of nephroblastoma. However, timing of each part of the treatment differs, in various protocols: the Societe Internationale d'Oncologie Pediatrique (SIOP) recommends the diagnosis based on imaging and metabolic exclusion of neuroblastoma to reduce the biopsy-related risk of spillage. In patients more than 6 months old, the treatment starts with the preoperative chemotherapy to improve the stage distribution at surgery and decrease the complications rate. Patients with advanced nephroblastoma, as those with vena cava thrombus and lung metastases, can benefit the most from the pretreatment. Results from the SIOP studies 6 and 9 confirm these statements: the stage distribution after the pretreatment reveals more than 50% of cases staged I, the 4-year disease-free survival in pulmonary stages IV was 83%, and of 42 patients with vena cava thrombus still present at surgery, 38 are alive from 27 to 109 months.