We cultured for Chlamydia trachomatis, Ureaplasma urealyticum, and Mycoplasma hominis and performed chlamydial serologic studies in 99 women undergoing laparoscopy. These women included patients with acute salpingitis, infertile women with and without mild pelvic inflammatory disease, and controls. C. trachomatis infection was significantly more common in patients than in controls. We also identified low-grade "silent" PID among women with infertility resulting from tubal obstruction and suggest this may be caused by chlamydiae.