In a prospective, randomized double-blind study the prophylactic effect of the immunotherapeutic agent, Gynatren®, against reinfection was investigated in 192 patients with bacterial vaginitis (95 treated with the active preparation versus 97 with placebo). In 30 and 25% of the patients in the two groups, respectively, it was the third or even more frequent infection in a period of 12 months. In a further 46 and 39%, respectively, it was the second infection in the course of a year. All the patients were given local treatment with tetracycline-amphotericin B vaginal suppositories and at the same time vaccinated with Gynatren or placebo. One month after the start of treatment, 85% of the patients in the active-treatment group and 83% in the placebo group were asymptomatic and free from pathogenic bacteria. After 3 months 78% in the active-treatment group and 60% in the placebo group were free from infection. After 6 months 76 and 40%, and after 12 months 75 and 37% of the women in the active-treatment and placebo groups, respectively, were free from clinical symptoms and pathogenic bacteria. These results correlated with the concentrations of local antibodies (secretory immunoglobulin) detectable in the vaginal secretion.