1080 nonpregnant women ages 16-34 years, presenting for the 1st time at a clinic for sexually transmitted diseases (STD), were examined and screened for infection with Chlamydia trachomatis, Neisseria gonorrheae, Trichomonas vaginalis, and Candida species. The respective prevalence rates were 21.1%, 20.7%, 13.4%, and 27.8%. Isolation rates for Chlamydia trachomatis, either occurring alone or in association with other genital infections, were significantly greater in women using oral contraceptives (OCs). This was not because OC users were more promiscuous. The findings strengthen the case for providing a routine chlamydial culture service for women attending STD clinics. They also indicate that the likelihood of chlamydial infection in women taking OCs is greater. (author's)