In an epidemiological survey of 2128 women attending a sexually transmitted diseases clinic for the first time and 200 attending two primary health clinics, 26% and 27% respectively were found to have bacterial vaginosis. The prevalence increased significantly with age, being diagnosed in 22.8% (326/1431) of women aged 14-24 years, and in 33.3% (232/697) of those aged greater than or equal to 25 years. Bacterial vaginosis was associated with gonorrhoea and with chlamydial infection, but was negatively associated with genital papillomavirus infection and yeast infection. Women using barrier contraceptives had a significantly lower prevalence of bacterial vaginosis than those using an intrauterine device or no contraceptive. Women less than or equal to 24 years old using oral contraceptives had a significantly lower prevalence of bacterial vaginosis than those not using contraceptives. Patients without gonorrhoea or chlamydial infection but with vaginal or urethral inflammatory signs had a significantly higher prevalence of bacterial vaginosis than those without inflammatory signs. These findings may have implications regarding complications associated with lower genital tract infections and may strengthen the hypothesis that bacterial vaginosis is a risk factor for pelvic inflammatory disease.