Gut bacteria are involved in the metabolism of a large number of biologically active substances, thus affecting all organs and tissues in the human body. Bile acids are also biochemically converted by the intestinal microbiota. For the prevention and treatment of diseases such as non-alcoholic fatty liver disease, cholelithiasis, metabolic syndrome, it is extremely important to understand the processes of formation, transformation and excretion of bile acids with the participation of the gut microbiota, which is discussed in this article. The study of the mutual influence of bile acids and bacteria is an important task of modern medicine, in the future, allowing the development of new approaches to the treatment of a range of diseases.