Microflora isolated from cattle with acute postnatal pus-catarrhal endometritis has been studied. It is shown that the given pathology is caused by associations of different bacterial species. 284 strains isolated from the uterus content of 63 sick animals have been identified, their properties being studied. Pathogenic gram-negative bacilli and gram-positive pus-producing cocci are responsible for the studied pathology. Considerable inoculation capacity has been established for conditionally pathogenic microorganisms of different species and genera whose role in pathogenesis is to be found out.