An indirect immunofluorescence test was used to determine the titre of serum antibodies to Candida albicans in 300 female patients. Titres from 1:4 to 1:6 were detected in 85 uninfected subjects and nineteen subjects with gonococcal infection. Titres from 1:4 to 1:16 were also detected in 166 of 169 patients found to be harbouring C. albicans, C. parapsilosis, or C. tropicalis in the digestive tract, genital tract, or both, without overt clinical infection. Titres from 1:32 to 1:128 were detected in one of four patients with vaginal candidiasis as compared with eleven of 23 patients with vaginal candidiasis who were also harbouring C. albicans or C. parapsilosis in the digestive tract. It is emphasized that titres of less than 1:32 did not preclude vaginal candidiasis.