Proton therapy is a promising new technology in radiation medicine. This issue of Radiation Medicine Rounds provides a comprehensive review for practitioners on the current status of proton therapy, its scientific basis and current clinical applications along with reviews of the available clinical evidence, discussions of costs and technology development, and reviews of the issues in establishing a proton therapy center and the future development of proton therapy as a tool in clinical practice, both in academic centers and its future potential in community practice. About the Series: Radiation Medicine Rounds is an invited review publication providing a thorough analysis of new scientific, technologic, and clinical advances in all areas of radiation medicine. There is an emphasis throughout on multidisciplinary approaches to the specialty, as well as on quality and outcomes analysis. Published three times a year Radiation Medicine Rounds provides authoritative, thorough assessments of a wide range of "hot topics" and emerging new data for the entire specialty of radiation medicine. Features of Radiation Medicine Rounds include: *