Conformal radiation therapy represents a new challenge for radiation oncologists. It offers the prospect of either increasing the radiation dose to target tissues while delivering a similar dose to organs at risk, or reducing the dose to organs at risk while maintaining the dose to target tissues. First, lymph node areas at risk are established using the available data from pathological examination of surgical specimens and/or pattern of locoregional relapse. Then, based on a three-dimensional description of the anatomical regions where the areas at risk are located, guidelines for the delineation of the clinical target volumes are proposed. The data presented should enable the reader to make appropriate decisions regarding the selection and delineation of the target volumes when confronted with the most frequent tumor types and sites.The book will contribute to paving the way for more effective radiation oncology in the twenty-first century.