This chapter introduces the principles and definitions of quality management systems (QMSs) for radiology facilities, to give a framework to assist in the setting up of such systems and to emphasize the role of the medical physicist in this context. While there is a diversity of terms currently in use to describe quality processes both generally and specifically within radiology, there is broad agreement that the effective management of radiation medicine services demands a quality culture that includes a systematic approach to the elements that govern the delivery of that service. Therefore, the concept of quality assurance (QA) within the radiological facility covers, in its widest sense, all those factors that affect the intended outcome, that is, a clinical diagnosis. The medical physicist has an important role in the overall QMS, especially, but not exclusively, with respect to the equipment performance. A worked example of a quality control (QC) programme is included at the end of the chapter, to demonstrate the depth of detail and involvement of the medical physicist.