The facultative and strictly anaerobic vaginal microbial flora was investigated in 40 women with non-specific vaginitis and in 40 control women seen in private gynaecological practice. Gardnerella vaginalis, anaerobic gram-negative bacilli, anaerobic gram-negative and gram-positive cocci were all associated with non-specific vaginitis (p less than 0.001), whereas lactobacilli occurred less frequently in non-specific vaginitis than in controls (p less than 0.01). The most common anaerobes were Veillonella parvula, Bacteroides bivius, Bacteroides assaccharolyticus, Bacteroides capillosus and Peptococcus asaccharolyticus. Anaerobic gram-negative curved rods were found in 11% of cases of non-specific vaginitis. A characteristic pattern of short chain organic acids was found on gas liquid chromatographic analysis of vaginal secretions in non-specific vaginitis. A succinate/lactate peak ratio of 0.3 or more was found in 75% of women with non-specific vaginitis (p less than 0.001). Clue cells, a positive amine test, a pH higher than 5.0, and the absence of lactobacilli on a Gram stained vaginal smear strongly correlated with non-specific vaginitis (p less than 0.001).