We determined the histologic correlates of clinically identified mucopurulent cervicitis, culture-proven cervical infection with Chlamydia trachomatis, Neisseria gonorrhoeae, herpes simplex virus (HSV), and vaginal infection with Trichomonas vaginalis by examining cervical biopsies from 83 women. Clinical mucopurulent cervicitis and culture-documented infection with one or more of these pathogens correlated histologically with intraepithelial neutrophils, reactive endocervical cells, edema, luminal neutrophils, and with several deeper tissue changes such as extensive and dense subepithelial inflammation, granulation tissue, and necrotic ulceration. Focal loss of surface columnar cells and spongiosis were also correlated with culture-confirmed infection. Well-formed germinal centers were seen in biopsies from 14 of 21 patients (67%) with C trachomatis infection alone, but in none of 17 patients with infections other than C trachomatis (P less than 0.001). A predominantly plasmacytic infiltrate was also significantly associated with chlamydial infection. Necrotic ulcers overlying a predominantly lymphocytic infiltrate were seen in six of nine patients (67%) with HSV infection alone but in only two of 40 patients (5%) with other infections (P less than 0.001). Marked inflammatory changes were not seen in the patients infected with N gonorrhoeae. The organism T vaginalis was not associated with any endocervical pathology. If these results are confirmed by prospective studies, they suggest that pathologists should alert clinicians to the possibility of recent or current infection with C trachomatis or HSV when cervical biopsies show the above changes. The loss of surface columnar epithelium with HSV, chlamydial, and gonococcal infection offers a possible explanation for the reported association of these infections with increased risk of acquiring human immunodeficiency virus infection.