The grivet monkey was used as an experimental model for vaginitis. Gardnerella vaginalis was used for challenge in one monkey. G. vaginalis plus a long variant (LCR) of a hitherto unclassified anaerobic curved rod (CR) in another 2 monkeys, this LCR alone in 2, a short variant (SCR) of CR in 2, and G. vaginalis plus SCR in one monkey. All the bacterial strains had been isolated from human vaginal specimens. In the 2 monkeys exposed to G. vaginalis plus LCR, distinct signs of bacterial vaginosis characterized by a thin, grey and translucent discharge appeared after 5 days and were still present at the end of the 6-week observation period. LCR alone produced, if anything, a slight increase in the vaginal discharge after about 4-5 weeks. In the remaining monkeys there was no increase of vaginal secretion. The CR could still be isolated at the end of the observation period. LCR persisted for 9 months in one monkey, without having produced any obvious signs of vaginitis, which, however, did appear when the monkey was challenged with G. vaginalis too. G. vaginalis could be recovered up to 12 days after incubation in the monkeys also infected with CR, but at no time from the monkey challenged with G. vaginalis only. Bacteria of the G. vaginalis morphotype could be observed in Gram-stained vaginal smears collected throughout the observation period. Although having certain limitations, the model would seem to be of use for the study of bacterial vaginosis. Such a model in primates has not hitherto been available.