60 women with bacterial vaginosis were entered into a double blind, placebo-controlled treatment trial with lyophilized Lactobacillus acidophilus. The lactobacilli used were producing H2O2. Immediately after completion of treatment, 16 out of 28 women who were treated with lactobacilli had normal vaginal wet smear results, in comparison to none of the 29 women treated with placebo. All women harboured Bacteroides at inclusion. Bacteroides was eliminated from the vagina of 12 out of 16 healthy women after treatment. Only three of the women who received the Lactobacillus suppository were free of bacterial vaginosis after the subsequent menstruation.