One or more hemolysins were demonstrated in soluble extracts prepd. by vibration in a Mickle tissue disintegrator from the yeastlike phases of Histoplasma capsulatum, Blastomyces dermatitidis, Candida albicans and Cryptococcus neoformans. The extract from H. capsulatum, which had the highest Kjeldahl N and the lowest total carbohydrate, had the highest hemolysin activity. The extracts from C. albicans and C. neoformans, which had no detectable Kjeldahl N and the highest total carbohydrate, had very little hemolysin activity. The hemolysin was most active against hen and guinea pig erythrocytes. Some properties of the hemolysin are described.