Women with recurrent vaginal candidosis were treated until the infection cleared and were then given one clotrimazole 500 mg vaginal tablet a month or an identical placebo as prophylaxis. Of 21 women who received placebo, 16 developed symptoms or signs within three months, compared with nine of 17 women given active treatment. Women who relapsed were treated and then given active prophylaxis once a month. Of 30 women given such treatment, 13 relapsed within three months. Women who relapsed were treated and then given two clotrimazole 500 mg vaginal tablets a month. Of 17 women given prophylaxis twice a month, four developed symptoms or signs within three months, but 10 remained clear for 12 months. No appreciable difference was seen in the incidence of mycological recurrence between the different regimens; within three months over half the women in all treatment groups had become recolonised.