OBJECTIVE: To investigate the possible involvement of human trichomonads (Pentatrichomonas hominis and Trichomonas tenax) other than Trichomonas vaginalis in the aetiology of vaginal trichomoniasis. METHODS: Vaginal swabs taken from women attending antenatal clinics were tested for Trichomonas vaginalis by traditional assays (wet-mount microscopy and InPouch culture) and nucleic acid amplification (polymerase chain reaction). These swabs were also tested for the presence of P hominis and T tenax by nucleic acid amplification. Oral and rectal swabs from these women were tested for T tenax and P hominis respectively. Data on sociodemographic characteristics, sexual and anogenital hygiene practices likely to seed P hominis and T tenax into the vagina were collected by a questionnaire. RESULTS: 93% (161) of the 173 samples in which T vaginalis was detected by wet preparation or culture was evaluable by PCR. Of this, T vaginalis was detected in 94% (152) by T vaginalis-specific PCR. Neither P hominis nor T tenax was detected in any of the vaginal swab samples. These included nine samples for which T vaginalis had been detected by wet preparation or culture, but were negative by T vaginalis nucleic acid amplification. P hominis and T tenax were not detected in any of the rectal and oral swabs, respectively. CONCLUSION: In this group of women, there was no evidence for the involvement of trichomonads other than T vaginalis in the aetiology of vaginal trichomoniasis.