The use of RT in pediatric cancer has been virtually eliminated in certain diseases (NHL); greatly reduced in some (Wilms' tumor, ALL, neuroblastoma); and refined and modified in others (rhabdomyosarcoma, Ewing's sarcoma). At present, however, it seems clear that RT will continue to be an important modality (particularly in brain tumors) and a much greater understanding of its effects has been achieved and utilized. The knowledge of the occurrence of late effects and SMN in a child cured of cancer is continuing to modify initial treatment strategies: A classic example of such an effort is the common use of lower RT doses and nonalkylator-based chemotherapy in Hodgkin's disease. Further, the use of DNA testing in children may be able to identify the presence of germline RB and p53 mutations, which may identify a child at high risk for SMN, so that appropriate therapeutic modifications may be made. In addition, knowledge of these late consequences in children mandates that they be carefully monitored and closely followed, so that prompt and effective treatment can be administered to give them a better chance for a long and healthy life.