The prevalence of trichomoniasis in Sydney was determined by examining 1070 sexually active females in three different practices. Infection rates ranged from 17.8% in a sympatomatic venereal-disease clinic group to 0.5% in non-promiscuous family-planning clinic patients. In each of these categories, the infestation rate, when compared with overseas reports, was lower but no explanation for this difference is apparent. Of the various laboratory methods used to detect Trichomonas vaginalis, the most sensitive was a culture method. The most convenient and reliable microscopy technique was phase-contrast microscopy which detected 80% of those with positive culture results. Stuart's Transport Medium will maintain trichomonad's viability for at least 24 hours and allow vaginal specimens to be reliably transported for examination.