In order to compare the vaginal microflora of women in prolonged pregnancy with that of women who delivered at term, samples for quantitative aerobic and anaerobic microbiological culture were collected from 100 women at 42 weeks of gestation and from 60 women at term. The occurrence of lactobacilli-dominated flora was similar in women at term and women with prolonged pregnancy. However, non-hydrogen-peroxide-producing lactobacilli (p < 0.01) were significantly more common and Peptostreptococci species (p < 0.05) significantly less common in postterm women as compared with term controls. In postterm women, Candida albicans was more common (p < 0.001) in microfloras dominated by non-hydrogen-peroxide-producing lactobacilli than in floras dominated by hydrogen-peroxide-producing lactobacilli. The ecosystem of the vagina in asymptomatic postterm women was disrupted concerning the composition of lactobacilli as compared with term controls.