The vaginal ecology of 463 community-dwelling postmenopausal women was characterized. Vaginal lactobacilli were present in 62% of the women and were significantly more prevalent among women receiving hormone replacement therapy during the previous year. Vaginal Escherichia coli and enterococci were each present in 39% of women and were significantly more frequent in women with a history of urinary tract infection. Heavy growth of lactobacilli was associated with a lower frequency of vaginal colonization with E. coli. Thus, postmenopausal women have a relative depletion of vaginal lactobacilli and an increase in vaginal E. coli compared with premenopausal women.