On the basis of morphology of colony, fermentation of certain carbohydrates and behavior to- wards milk, 150 cultures of Monilia isolated from cases of thrush, bronchitis and vaginitis, or secured from the American Type Culture Collection, variously named M. albicans, M. richmondi Shaw, M. psiolosis, M. pseudotropi-calis, etc., could be classified into 3 spp. Each species gives a characteristic colony morphology on malt agar plates in 48 hrs. The Type I species is seldom encountered. The largest number of the cultures belong to the species of which M. albicans is the type culture. An important characteristic of this species is its regularity in coagulating milk of pH 6.4, while milk of pH 6.8 or above is not coagulated. The 3rd species, of which M. Candida is the type culture, does not coagulate milk but always increases the pH, the milk becoming distinctly alkaline. The differential sugars for the 3 spp. are maltose and sucrose. Type I ferments neither maltose nor sucrose with gas production. The M. albicans type ferments maltose but not sucrose, while the M. Candida type ferments both maltose and sucrose with gas production. The cultural and biochemical characteristics proved constant after repeated tests over a period of 5 yrs.