Comparative microbiological investigations of biopsy specimens from the cervix of women with gynaecological infections, and from the cervix secretion of healthy women with normal menstrual cycles, as well as animal experiments were conducted in order to determine the pathogenicity of non-sporeforming anaerobic bacteria in the female genital tract. From the results the following conclusions were drawn: any anerobic bacterium is considered pathogenic if it is cultured in liquid or solid medium from a non-gravid uterus, the tubes or the exudate in the small pelvis. Bacteria isolated from the cervial canal during puerperium or from the uterus are considered pathogenic if a large number grows on solid culture and if a known pathogenic species predominates. Bacteria isolated from the vagina can be of pathogenic significance if the clinical findings are not normal and if the above-mentioned criteria are considered.