The purpose of ICRP Publication 73 is to clarify how the recommended system of radiological protection as described in the 1990 Recommendations of the International Commission on Radiological Protection should be applied in medicine. This report is addressed principally to physicians and physicists directly engaged in medical radiology, including diagnosis in medicine and dentistry, nuclear medicine and radiotherapy; to those responsible for the management of institutions operating in these fields; and to international regulatory and advisory bodies.