To the nutrient medium for fungi the whey fermented for 5, 9, and 14 days was added in the amount of 10-30%. The applied whey doses exerted a fungicidal effect or inhibited the growth of fungi colonies. The strongest fungicidal effect in relation to all the test organisms exerted wheys fermented for 14 days by P. jensenii, containing 497 moles/dm3 of both acetic and propionic acid jointly at the ratio of 1:3,3. Among the fungi tested it was Geotrichum candidum, which responded to propionic bacteria metabolites mainly with morphologic changes.