One thousand eight non-pregnant women aged 16-34 years, presenting for the first time at a clinic for sexually transmitted diseases (STD), were examined and screened for infection with Chlamydia trachomatis, Neisseria gonorrhoeae, Trichomonas vaginalis, and Candida species. The respective prevalence rates were 21.1%, 20.7%, 13.4%, and 27.8%. Isolation rates for C trachomatis, either occurring alone or in association with other genital infections, were significantly greater in women using oral contraceptive agents. This was not because oral contraceptive 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 oral contraceptives is increased.