Objective. To assess the composition of the microorganisms of the uterine cavity of women with chronic endometritis (CE) and idiopathic infertility. Materials and methods. The study included 145 women of reproductive age with idiopathic infertility. All the patients underwent hysteroscopic examination followed by biopsy histopathological evaluation for immunohistochemical (IHC) and microbiological («Femoflor 16» and «Femoflor Screen» test, DNA-technology, Moscow) studies. Results. According to the results of the IHC study, the CE was detected in 113 (77.9%) patients. The most common microorganisms identified in the uterine cavity were Lactobacilli (66.21%), as well as Staphylococcus (44.83%), Enterobacteriaceae family (22.1%), Ureaplasma spp. (19.3%), Streptococcus spp. (15.2%), Gardnerella vaginalis (11.03%), Atopobium vaginae (10.34%). The presence of Ureaplasma spp. in the uterine cavity significantly increasing the risk of developing CE by 4,5 times (RR=4.483; 95% CI 1.003–20.029). Presence of Atopobium vaginae and Staphylococcus spp. increases the risk of developing pronounced CE by 7 times (RR=6.959; 95% CI 0.856–56.602) and 2.5 times (OS=2.5; 95% CI 1.034–6.043), respectively. Conclusion. The risk of developing CE increases with the persistence of certain microorganisms in the uterine cavity.