Endometriosis is a multifactorial disease that affects mainly women of reproductive age. The exact pathogenesis of this disease is still a mystery. The analysis of modern etiology concepts and mechanisms of adenomyosis development were carried out. The review includes data from foreign articles published in the PubMed, UpToDate, eLibrary databases over the past ten years. A number of works presenting studies of the uterus microbiota and its influence on the disease development were analyzed. The possibilities of cultural and molecular genetic diagnostic methods, in particular 16S rRNA, in studying the state of the uterine cavity microbiota are described. The modern paradigm of the development and progression of adenomyosis provides for the presence of endometrium bacterial contamination which, in turn, is a trigger for cell modifications activating a vicious circle of pathology.