Hyposensitisation with a commercially available antigen has been attempted in the treatment of women suffering from recurring monilial vaginitis. Ten women entered the trial, each being used as her own control. Eight of them showed undoubted improvement and the average interval between relapses increased from 5.1 to 15.7 months (p. less than .01). Reasons are given for believing that allergic reactions play a part in recurrent vaginal thrush.