We studied 71 women with the clinical diagnosis of acute pelvic inflammatory disease (PID) by laparoscopy and comprehensive microbiology in order to define the major etiologic determinants of poor fertility prognosis after tubal infection. Fifty women were found to have acute PID. Of the 50 women, 23 were pregnancy seeking and had a subsequent evaluation to determine fertility outcome. Seven of 13 women with non-gonococcal infection had an adverse reproductive outcome, compared with none of 10 women with gonococcal infection (P = .007). Two groups of causes for adverse reproductive outcome were found. Of the seven infertile women, four had initial tubal abscess, and three had evidence of Chlamydia trachomatis infection. This study directly documents the poor fertility prognosis for women with tubal abscess and suggests that women with culture and/or serological evidence of chlamydial infection also have a poor fertility prognosis.