The presence of Chlamydia trachomatis antigen was examined in 400 endocervical samples collected from an equal number of asymptomatic sexually active women. The overall prevalence was found to be 4%, using the enzyme-linked immunosorbent assay. Chlamydia infection was correlated with younger age (5.8%, p < 0.05), a history of pelvic inflammatory disease (30%, p < 0.0001), and more than four lifetime sexual partners (7.9%, p < 0.01). Women who used oral contraception had more infections (9.7%), than did women who used the intrauterine contraceptive device (4.8%, p > 0.05), condom (0%, p < 0.01) or no contraception (3.1%, p < 0.05). Infection was strongly associated with cervical erythema (8.2%, p < 0.0001), ectopy (7%, p < 0.05), friability (20%, p < 0.0001), and endocervical discharge (100%, p < 0.0001). These results support the view that Chlamydia trachomatis infection is associated with younger age, intense sexual life, and use of oral contraceptives. Given that the majority of infected women revealed cervical pathology, the detection of chlamydia in the high-risk female population with cervical changes seems to be essential.