This handbook is designed to provide the radiation oncologist with clear practical guidance in the delineation of tumor volumes and/or radiation fields for a wide variety of pediatric cancers, including the most frequently encountered malignancies of childhood. This is a guide to designing treatment fields and volumes that may be utilized in the delivery of conformal therapies such as intensity-modulated radiation therapy and proton therapy, the latter being particularly relevant in children. Each chapter focuses on a specific tumor type, providing general guidelines that will assist the reader in delineating the clinical target volume for particular presentations, including patterns of spread.