The manual summarizes the fundamental provisions of the modern theory of epidemiology of infectious diseases, integrating both the foundations of the classical theory and the results of their own and other recent domestic and foreign research in this area. The principles of preventive and anti-epidemic measures are outlined, the legal aspects of the epidemiologist's practical activities are considered. For epidemiologists, infectious disease specialists, organizers of the state sanitary and epidemiological service, health care and science, students and teachers of medical educational institutions.