Cervical abnormalities accompanied by Papanicolaou Class II or Class III cytologic results are commonly encountered in gynecologic office practice. Chlamydiae are a common cause of genital tract infection, with or without manifest symptoms or signs. An immunofluorescence method was used to determine the presence of antichlamydial antibodies in cervical secretions. Eleven of 15 patients in whom such antibodies were found (73.3%) had Papanicolaou Class II or Class III smears, in contrast to only 3 of IS patients (16.7%) without antichlamydial antibodies. The determination of antichlamydial antibodies in cervical mucus was highly reproducible, and specimens were readily collected in the office, without the need of prompt laboratory procedures. In selected patients, tetracycline treatment of early chlamydial infection resulted both in the disappearance of the antibody from cervical secretions and in the reversion of the Papanicolaou smear from Class II or Class III to Class I.