What are the limitations to the accuracy of our current technologies in radiation oncology? The immobilization of the patient, definition of the target, motion of the target and localization of the target are the major concerns that must be addressed. Current approaches to meet these needs have brought new technical systems with greater precision and new clinical procedures with higher expectations of practice. This text offers discussions on these issues, including advances in intensity-modulated radiotherapy planning, clinical target definition for the major tumor sites, management of organ motion, target localization and image guidance systems, and the expanding applications of high-precision treatment with stereotactic body radiotherapy.