The EC (European Commission) Directive on radiation protection of patients requires that Criteria for Acceptability of Equipment in Diagnostic Radiology, Nuclear Medicine and Radiotherapy be established throughout the member states. This paper reviews the background to this requirement and to its implementation in practice. It notes parallel requirements in the EC medical devices directive and International Electrotechnical Commission standards. It is also important to be aware and that both sets of requirements should ideally be harmonised due to the global nature of the equipment industry. The paper further reviews the type of criteria that can be well applied for the above purposes, and defines qualitative criteria and suspension levels suitable for application. Both are defined and relationships with other acceptance processes are considered (including acceptance testing at the time of purchase, commissioning and the issue of second-hand equipment). Suspension levels are divided into four types, A, B, C and D, depending on the quality of evidence and consensus on which they are based. Exceptional situations involving, for example, new or rapidly evolving technology are also considered. The publication and paper focuses on the role of the holder of the equipment and related staff, particularly the medical physics expert and the practitioner. Advice on how the criteria should be created and implemented and how this might be coordinated with the supplier is provided for these groups. Additional advice on the role of the regulator is provided.