The term "blastomycosis" is often applied to any disease in the lesions of which the causative fungus appears as rounded cells more or less resembling those of yeast. Consequently this designation has been used for different mycoses which have little clinical or pathologic similarity and which are caused by unrelated species of fungi. On the other hand, different names are applied by different clinicians to what are evidently infections by the same fungus. The terminology of the fungi concerned is even more chaotic. The first step necessary toward clearing this confusion and obtaining an orderly understanding of these infections appears to be a careful study of the causative fungi and the establishment of criteria by which distinct types may be recognized. The present report is based on a study of fungi from three important types of mycotic infection. TYPE I: CRYPTOCOCCUS HOMINIS (BUSSE AND BUSCHKE 1894) (VUILLEMIN, 1901) Cryptococcosis.— In