Abstract 1.1. The clot-peptone broth in rubber-stoppered vaccine bottles permits preservation of yeast phase cultures of Blastomyces dermatitidis, Histoplasma capsulatum, and Sporolrichum schenkii for at least 2 years without transfer. 2.2. The same organisms will convert from filamentous inoculum to yeast phase after extended incubation at 37° C. 3.3. Cultures can be recovered easily in either yeast phase or filamentous form without destroying the original stock preparation. 4.4. The medium is practical for the quantity production of yeast phase growth of these organisms, and may prove equally useful for the long-term preservation of other fungi and bacteria.