One hundred and two cervical biopsy specimens containing varying degrees of chronic inflammation were stained for chlamydial antigens with the immunoperoxidase technique. Seven cases (6.9%) were positive. Histologically, six (84%) of the Chlamydia-positive cases contained severe chronic inflammation, all contained reparative atypia, and two (28%), follicular cervicitis. When evaluated separately, 22% (six of 27) of the specimens with severe inflammation were positive in contrast to 0% (0 of 45) of cases with mild inflammation. Positively staining cells were located primarily in columnar epithelium and reparative atypia and occasionally in areas of immature squamous metaplasia. The cytological finding which correlated with positive staining was cytoplasmic vacuolation; however, cytoplasmic vacuoles were common in cells which did not stain positively, and it was impossible to predict on histological grounds which cells/specimens would stain positively by immunoperoxidase. Because of these findings, the presence of chlamydial infection should be strongly suspected whenever the cervical biopsy specimen contains severe inflammation and repair. Although tissue staining may not be as sensitive as culture for diagnostic purposes, it can be performed rapidly and simply and may be a useful special stain in cases where the diagnosis of chlamydial infection is not suspected clinically or cultures are not immediately available.