Two hundred patients suffering from vaginal Trichomonas vaginalis infection were admitted to a double-blind clinical study. All patients provided a detailed history of previous episodes of vaginitis. All women were treated with one dose of nimorazole 2 g stat. In addition, one group of patients were vaccinated with SolcoTrichovac and the other group received a placebo ‘vaccination’. The immediate effect of the nimorazole treatment was comparable in both groups, relapses and reinfections, however, differed significantly after 4 weeks (p < 0.01) in favour of the SolcoTrichovac group. After 4 and 8 months, the effect of the vaccine in preventing reinfections was even more pronounced, with a statistical difference of p < 0.001 between the two groups of patients.