A prospective study of genital infections was conducted in a university-affiliated teaching hospital in Hamedan City, Iran. A total of 540 women were recruited and divided into two equal groups: (1) the case group with vaginitis (N=270) and, (2) the asymptomatic control group (N=270). Participants were interviewed about the occurrence of any vaginal or urethral discharge. Two vaginal swabs were obtained for pH testing, KOH and wet mount examination, Gram staining and culture at the time of speculum examination. In the case group, the prevalence of candidiasis, trichomoniasis, and bacterial vaginosis was 17.2, 18.1, and 28.5%, respectively. Measurement of vaginal pH in the clinic was the single most useful clinical finding for directing empirical therapy. No single specimen was found ideal for all pathogens; a cervical swab is better for Trichomonas vaginalis but a vaginal swab is needed for candida and bacterial vaginosis. To achieve STD control in this and similar populations, public health programs must target asymptomatic infections.