Intermittent treatment with an acid lactate gel (Lactal, ACO, Sweden) reduced symptoms of bacterial vaginosis (BV) and promoted the reestablishment of the normal vaginal flora of lactobacilli. Forty-two women seriously affected by recurrent BV were initially given acid gel (lactate gel, pH 3.8, 5 ml) to be inserted into the vagina daily for 7 consecutive days. Thereafter they entered into a double blind clinical trial and were treated prophylactically 3 days monthly for 6 months with either lactate gel or a placebo gel. Women treated with the lactate gel were clinically improved, i.e. no signs of BV in 88% compared to 10% in the placebo group (p less than 0.001). The vaginal lactobacilli flora was reestablished in 83% of the lactate group and in 16% of the placebo group. Local intermittent application of lactate gel was found to be free of side effects and is a preferable alternative to repeated treatments with antibiotics in patients with recurrent BV.