Several new genitourinary Bacteroides species and the new Mobiluncus/Falcivibrio have been described since 1977. The normal vaginal flora consists mainly of lactobacilli and other "non-pathogenic" aerobes and anaerobes. Under unknown circumstances, organisms may increase in number, displacing the normal lactobacillus flora and raising the vaginal pH. This renders a more favourable biotope for organisms with a pH optimum in the neutral or alkaline range. Overgrowth of Gardnerella, Bacteroides, B-streptococci and Mobiluncus/Falcivibrio is indicative of vaginosis, which is not a typical sexual disease, but may be sexually transmitted. Proper treatment includes the male partner. No overall-valid therapy exists, but metronidazole is the drug of choice if Bacteroides or Gardnerella form the disturbed flora, and beta-lactams are the drugs of choice when Mobiluncus or aerobes are involved.