Mycoplasma hominis is isolated from the cervix of 10-20% of healthy, fertile women. In contrast, the organism is recovered from the lower genital tract of 50-70% of women with pelvic inflammatory disease. Moreover, a significant antibody response to M. hominis is found in one-fourth of all patients with clinical and/or laparoscopic signs of pelvic inflammatory disease. These results suggest that M. hominis is etiologically involved in inflammation in approximately 25% of patients with acute pelvic inflammatory disease and in approximately 40% of women from whose cervix the organism is isolated.