[en] The purpose of this document is to improve existing radiological care by providing physicians with information that can lead to a reduction in unnecessary medical radiation exposure to the population. In general, attending physicians are responsible for selecting patients for x-ray examinations. In exercising this judgement, they determine the volume and distribution of diagnostic x-ray examinations. The areas of x-ray utilization and efficacy are constantly undergoing research and investigation. By accelerating the application of the results of such studies in selecting patients for x-ray examination and by being concerned over the actual conduct of examinations, attending physicians can exercise considerable positive influence over the radiation dose to the population. This manual discusses the biological, physical, and social issues related to patient selection, which directly and indirectly influence a physician's decision each time he considers requesting an examination