A study of 552 female patients was undertaken to determine the frequency of yeast infections in women attending a V.D. clinic. The findings were as follows: (1) 207 of the 552 (37.5 per cent.) were found to have yeasts. (2) C. albicans accounted for 86 per cent. of these yeasts. (3) There was no difference in incidence related to age or seasonal variation. (4) Oral contraceptives increased the incidence of yeasts (43.2 per cent. on "the pill"; 33.2 per cent. not on the pill"), but the incidence of Trichomonas was decreased (6.8 per cent. on "the pill", 19.3 per cent. not on "the pill"). (5) Previous antibiotics also contributed to the incidence; 23.2 per cent. of patients with yeasts had had antibiotics previously compared with 13.6 per cent. of those without yeasts. (6) Other infections were associated in seventy cases (33.8 per cent.). (7) Culture is essential for the detection of yeasts; 64 per cent. were positive only on culture. (8) Symptoms were present in 70 per cent. of patients with yeasts. (9) 93 male consorts were seen and in 31 (33 per cent.) yeasts were detected by smear, or culture. Of the 47 in whom cultures were examined, 23 (49 per cent.) were positive. The general factors affecting the incidence of yeasts are discussed as well as the differentiation of the saprophytic from the pathogenic role of yeasts. It is suggested that asymptomatic yeast infections are often best treated, but that each case should be considered individually. Male consorts should also be treated to prevent re-infection.