This study investigates the prevalence of Chlamydia trachomatis antibodies in 164 infertile women who underwent diagnostic laparoscopy and dye insufflation as part of routine infertility investigations. C. trachomatis antibodies were found in 36 (22%) of 164 infertile women, which was significantly more than the prevalence of antibodies in a control group (22 of 200, 11%). C. trachomatis antibodies were found in 25 (35.7%) of 70 infertile women who had laparoscopically verified peripheral tubal disease. This was significantly more than the prevalence of C. trachomatis antibodies in infertile women with normal fallopian tubes (6 of 52, 11.5%). The prevalence of C. trachomatis antibodies in infertile patients with laparoscopically verified cornual disease was similar to those without cornual disease. C. trachomatis was not isolated from any of the patients studied. This study confirms that past chlamydial salpingitis is associated with the development of peripheral fallopian tube obstruction with resultant infertility.