The polymicrobial nature of pelvic inflammatory disease (PID) underscores the need for a clearer understanding of the pathogenesis and etiology of PID especially among core groups most at risk. This study was designed to determine the role of specific microbial infections in leading to PID among women. Prevalence of genital chlamydial infection and other reproductive tract infections were determined in 100 women presenting at a health facility at Port Harcourt, Rivers State, Nigeria. The result showed that 11.1 per cent of women with acute PID were infected with Chlamydia trachomatis as compared to 4.3 per cent in the control group (odds ratio 2.75: 95% confidence interval (CI), 0.7-11.7). Neiserria gonorrhoeae was not detected in either of the two groups. Trichomoniasis (10% in PID cases and no case in control group) and bacterial vaginosis (17.5% and 4.3% in PID and control group respectively: Odds ratio 4.7, 95% CI, 1.0-21.1) were also significantly associated with the clinical picture suggestive of acute PID. It is recommended that where resources are limited, patients presenting with acute PID be treated empirically for Chlamydia trachomatis, trichomoniasis, bacterial vaginosis and gonorrhoea.