Clinical trials in radiation oncology are the best vehicle to optimize our strengths in therapeutic technology, define progress in our field, and improve patient outcome. Trials advance our knowledge in each disease site and provide us information to improve the radiation dose-volume for both tumor control and therapeutic sequelae to normal tissue. An increasing number of systemic and targeted therapies have been developed and are currently in early phase clinical trial design. Ultimately, these new therapies will need to be tested with standard-of-care therapy including radiation oncology. Therefore, during a study, it is essential that radiation therapy is delivered in a uniform and consistent manner for the credibility of the study. If the radiation therapy component of the study does not have a structure or management for maintaining therapeutic compliance, including a real-time data management strategy, it becomes difficult to trust the study outcome and apply the outcome to daily clinical practice. In this chapter, we review the strategy and process involved in the management of dosimetry in radiation oncology clinical trials and how this can impact clinical trial management, primary study endpoints, and the overall success of the study.