[en] The largest group of individuals exposed occupationally to artificial radiation sources is that employed in health facilities. These individuals include: radiologists; radiation oncologists; other physicians who use X rays and radionuclides in their practices; other practitioners, such as dentists, paediatricians and chiropractors, who are licensed to use X rays; radiographers and radiological technologists who assist in the production of images and the management of patients; radiological physicists; installers; repairmen; and inspectors and regulators. The training and qualifications of these groups of users vary from country to country and from profession to profession. In most countries, recognized qualifications are a combination of governmentally set minimum standards and professional qualifications. However, some disciplines which are legally allowed to use X rays for medical applications have no training requirements for their members in this respect and in some countries the state of medical practice requires that those available learn about X ray uses on an ad hoc basis without any formal training or qualifications. There is no international authority which keeps records on the numbers, locations or qualifications of medical user groups. Some estimates put the number of 'qualified' physician users at about 200,000 and the number of radiographers/radiological technologists at perhaps 500,000. Taking all other medical radiation users into account, the total might reach close to a million people. International and national bodies have recommended maximum occupational exposures for radiation workers which apply to medical users. Modern X ray and isotope handling equipment is provided with built-in shielding and beam limitation devices. Radiation training, where it is provided, emphasizes good radiation hygiene, dose limitation, beam collimation and careful attention to image processing. The modern capabilities of imaging with ionizing radiation are such that the volume of medical usage increases significantly. Furthermore, some recently introduced diagnostic procedures have the potential to give unacceptable doses to patients and higher than acceptable occupational exposures to the physicians and technologists involved. Achieving the aims of the medical use of radiation with a minimum of risk both to patients and practitioners requires a continuing, multilayered approach involving both national and international health agencies and professional and educational organizations. A successful radiation safety programme is a calculated mix of education and regulation. The need is continual and a commitment of intent and resources is necessary. (author)