In a group of 55 unmarried women, mean age 25 years, attending a family planning clinic and having minor gynecological complaints, the correlation between Chlamydia trachomatis (CT) antigen, CT antibodies, vaginal colonization by Candida or bacteria and the method of contraception was investigated. The correlation between CT antigen and CT antibodies (IgG) was significant in oral contraceptive users (p = 0.003), as was the correlation with vaginal colonization by Candida and potential pathologic bacteria. In the group using the natural family planning method, a statistically significant correlation was found between CT antigen, IgG (p = 0.002), IgA (p = 0.02) antibodies, and vaginal candidiasis (p = 0.002), but not with bacterial colonization (p = 0.90). The discrepancy between CT antigen and antibodies is discussed. Differences in the prevalence of Chlamydia trachomatis infection were found among groups using different birth control methods, indicating an association between Chlamydia infection and the contraceptive method used.