The role of radiotherapy in multiple modality treatment of Wilms' tumor is evaluated in 225 children aged 3 months to 11.5 years (mean age 3.5 years) with stage III-IV. 184 (81.8%) patients presented with stage III, 93.7% with typical nephroblastoma. Intervention was combined with drug and radiotherapy in 99.6% patients. Exposure of the abdominal cavity in total focal doses of 10.5-50.2 Gy (mean dose 28 Gy) was carried out in 219 (97.3%) of 225 patients. Special attention is paid to the incidence of relapses, remote metastases, and survival of patients in relation to prognostic factors (sex, age, stage of tumor process, terms of exposure, and total focal doses). All patients were followed up for 2-203 months (median 32 months). During this period relapses and/or metastases were observed in 34.2% patients; 30.2% died because of disease progress. 35.1% children live without signs of disease for more than 5 years, 14.7% for more than 10 years. Relapses were more incident during the first year of treatment (in 65% children) and outside the exposed field (72.5% cases). 33.2% patients with stage III developed metastases after 1-49 months; the lungs were involved most often. Prolongation of the period between surgery and exposure of the abdominal cavity led to increase in the incidence of relapses in the abdominal cavity from 6.7% (up to 2 weeks) to 21.9% (more than 1 month), p = 0.02. Relapses were the most frequent in children aged over 4 years. This parameter virtually did not depend on the total focal dose. The absence of relationship between the incidence of local relapses and life span after exposure to a total focal dose of up to 21.6 Gy in comparison with higher doses recommends reduced doses for therapy without notable deterioration of the survival of patients with nephroblastoma.