In 350 pancervico-vaginal (Fast) smears obtained from women using intrauterine contraceptive devices, organisms consistent with Actinomycetes have been found. Actinomycetes, representing cervicitis, endometritis, and pelvic abscesses clinically, have been observed histologically in some of these cases. Special stains, immunofluorescence, and anaerobic cultures have confirmed these organisms to be Actinomyces israelii. Actinomyces in the Fast smear occur in isolated clumps, revealing branching, filamentous organisms, and sulfur granules. They can be detected and diagnosed in a Papanicolaou-stained routine pancervico-vaginal smear. This diagnosis in Fast smears can identify users of intrauterine contraceptive devices who may have Actinomyces infection in the genital tract and who are at risk of developing clinical disease related to this infection.