Purpose: To determine if previous exposure to chlamydia, as evidenced by positive serology, is associated with a greater degree of detectable hydrosalpinges, and to determine if positive serology is more associated with bilateral than unilateral hydrosalpinges. Materials and Methods: Retrospective study evaluating all patients who had either a unilateral or bilateral hydrosalpinges detected by laparoscopy. The group was further defined by these women in this group who had serum chlamydia antibody tests and transvaginal pelvic sonography (TVS). Results: Prior exposure to chlamydia infection as evidenced by positive serology was detected in 31 of 39 (79.4%) women . All eight women with negative serology had a unilateral hydrosalpinx, of which only one could be detected by TVS. Whereas 29.4% of 17 women with unilateral hydrosalpinges and positive serology were detectable by TVS, 35.7% of the 25 hydrosalpinges of the 14 women with positive serology and bilateral hydrosalpinges could be detected by TVS. TVS correctly identified 16 of the 53 (30.2%) hydrosalpinges seen by laparoscopy. TVS identified 15 of the 39 (38.5%) women who had at least one hydrosalpinges. Conclusions: Ultrasound alone will detect less than 50% of hydrosalpinges, since women negative for chlamydia exposure are more likely to have smaller unilateral hydrosalpinges not detected by ultrasound. Future studies are needed to determine if salpingectomy may not be needed to improve fecundity.