Aim. The purpose of this study was to analyze the microbiological aspects of chronic endometritis in women with a history of reproductive loss. Materials and methods. The study involved 480 women with a history of non-developing pregnancy, spontaneous miscarriage, artificial abortion, IVF failure with pathomorphologically verified CE (retrospective and prospective analysis). Microbiological research and DNA diagnostics of possible pathogens of CE, determination of embiotropic autoantibodies in blood serum (ELI-P-test), hysteroscopic and pathomorphological studies (aspirates and biopsies from the cervical canal and uterine mucosa) were carried out. Results. During the study it was found out that the persistent conditionally pathogenic flora is likely to lead to progressively worsening changes in the general immune status, and the impaired immune resistance creates favorable conditions not only for the further growth of infections that caused the pathological process, but also for the involvement of new types of microorganisms in it (formation vicious circle). In this regard, CE is often characterized by polymicrobiality. In this case, there is a loss of the clinical specificity of the infectious process, which complicates both the diagnosis and the choice of adequate antibiotic therapy. Keywords: chronic endometritis, macrotypes, diagnostics, autoantibodies, infection, microflora.