Anaerobic bacteria constitute a substantial component of the normal vaginal flora and of the outer cervical canal. Consequently, one would expect infections emanating from the vaginal flora to be caused to a substantial degree by anaerobic bacteria. The anaerobes may contribute in colpitis, but their role is difficult to prove in this situation, since sampling only yields normal flora components. One clue that anaerobes may contribute to colpitis is the circumstance that the flora under those conditions differ from the normal situations. Another is the circumstance that metronidazole, which only inhibits anaerobes, does reduce symptoms e.g. of colpitis in the presence of the microaerophilic Gardnerella vaginalis, which is resistant to metronidazole (but sensitive to the metabolite hydroxymetronidazole). In the US, pelvic inflammatory disease (PID) is to a substantial degree apparently caused by anaerobic bacteria. Our experience in Scandinavia indicates that anaerobes are of neglible importance in this condition, since we rarely isolate anaerobes in spite of adequate sampling, transport and processing of specimens. We mostly find anaerobes in post-operative PID when the vaginal wall has been passed, or as a complication of pregnancy (puerperal fever, early rupture of membranes, abortion), and in connection with intrauterine devices. The role of anaerobes in bartholinitis is established. PID may be associated with appendicitis or colonic diverticulosis. Anaerobes are regularly isolated from abscesses developing in the pelvic organs. This also applies to tuboovarial and vulvovaginal abscesses. The most important anaerobic bacteria in infections of the female genital organs are Bacteroides fragilis and other species of the fragilis group, B. melaninogenicus and related species, other Bacteroides, peptococci and peptostreptococci. Clostridium perfringens rarely cause infections of female genital organs, although such conditions have a dramatic course.