Forty-two cases of non-metastatic Wilms tumor, treated at Dept. of Radiation Oncology, Yonsei University College of Medicine, Yonsei Cancer Center, between January 1970 and September 1984 were retrospectively analysed. With the introduction of well-planned multimodality concept, 26 patients were treated in this manner (group A), and multimodality treatment consist of surgery, radiotherapy, and chemotherapy and details of treatment regimen are described. Prior to introduction of multimodality concept, 16 patients were treated by rather individual basis with diversities of multimodalities which was not well-planned (group B). Two year relapse free survival rate of group A and group B was 88% and 31%, respectively (p< 0.05). By stage in group A, 2 yr. RFS for stage I, II, and III showed 92%, 88%, and 80%, respectively. The most significant prognostic factor was histologic subtype, i.e., favorable vs, unfavorable histology (p<0.005). Other prognostic factors included weight of tumor mass and status of lymph node involvement (p<0.05). From this study it can be concluded that; 1. well-planned multimodality approach to Wilms tumor can produce far superior survival relative to that of not well planned, 2. similar good results can also applied to even in the advanced stage, 3. significant prognostic factors are histologic subtype, weight of tumor mass, and status of lymph node involvement.