The paper gives the definition, goal, and objectives of clinical epidemiology. The latter is shown to be an epidemiology section that makes it possible to elaborate evidence-based standards for diagnosis, treatment, and prevention and to select a respective algorithm of actions for each specific clinical case. Randomized controlled trials are the gold standard for obtaining evidence. Scales are proposed to evaluate the efficacy of preventive and therapeutic agents: the levels of evidence for their efficacy and the level of strength of its evidence. The authors propose to set up clinical epidemiology centers, one of whose goals should be to introduce a unified system to evaluate the efficacy of preventive and therapeutic agents, by using the principles of evidence-based medicine and the methods of clinical epidemiology.