We studied the vaginal microflora of 73 postmenopausal women who had never received estrogen replacement therapy. The median age of these women was 67 years, and none of them had bacterial vaginosis. Lactobacilli were detected in 36 (49%) of these women at a mean concentration of 10(5.7) cfu/g of vaginal fluid. H2O2-producing lactobacilli were recovered from 38% of the women. Some of the other organisms that were recovered, including Gardnerella vaginalis (27% of the women), Ureaplasma urealyticum (13%), Candida albicans (1%), and Prevotella bivia (33%), were less frequently isolated from postmenopausal women than from women of reproductive age, while coliforms (41%) were recovered at higher frequencies. Lactobacilli, yeasts, and bacterial vaginosis-associated bacteria are less commonly part of the vaginal microflora in postmenopausal women than in women of reproductive age, which may explain the decrease in the incidence of bacterial vaginosis and yeast vaginitis among these women.