The textbook contains basic information on all sections of radiation medicine: basics of physics of ionizing radiation, radiation dosimetry, radiometry, radiation safety, information on the radiation situation that developed after the Chernobyl accident. The question of the influence of ionizing radiation on the human body is considered, the information on radiation sickness, low doses effects and long-term consequences of ionizing radiation is given. The issues of population dispensary examination and maintenance of the State Register are covered. Particular attention is paid to the modern concept of anti-radiation nutrition and means that promote the elimination of radionuclides from the body. The textbook is written in accordance with the program of the discipline “Radiation Medicine” for the training specialists of the second (Master's Degree) level of higher education according to the requirements for textbooks for students of higher medical education of Ukraine III–IV levels of accreditation. It may be useful for interns, clinical residents and university students in the study of disciplines of general biological and ecological profiles.