OBJECTIVE To evaluate the endometrial microbiology and histopathology in women with symptomatic bacterial vaginosis but no signs or symptoms of upper genital tract disease or other vaginal or cervical infections. METHODS Endometrial biopsies were performed on 41 women complaining of vaginal discharge or pelvic pain at a sexually transmitted disease clinic. These women had neither culture nor serologic evidence of Neisseria gonorrhoeae or Chlamydia trachomatis infection. Twenty-two women with bacterial vaginosis diagnosed by Gram stain examination of vaginal fluid, but with neither signs nor symptoms of upper genital tract infection, were compared with 19 women who had no evidence of bacterial vaginosis on vaginal fluid Gram stain. Endometrial biopsies were evaluated for histopathologic evidence of plasma cell endometritis and were cultured for N gonorrhoeae, C trachomatis, aerobic and anaerobic bacteria, Mycoplasma species, and Ureaplasma urealyticum. RESULTS Ten of 22 women with bacterial vaginosis had plasma cell endometritis, compared with one of 19 controls (odds ratio [OR] 15, 95% confidence interval [CI] 2-686; P < .01). Bacterial vaginosis-associated organisms were cultured from the endometria of nine of 11 women with and eight of 30 women without plasma cell endometritis (OR 12.4, 95% CI 2-132; P = .002). CONCLUSION Plasma cell endometritis was frequently present in women with bacterial vaginosis and without other vaginal or cervical infections. This suggests the possibility of an association between bacterial vaginosis and nonchlamydial, nongonococcal, upper genital tract infection.