We observed for the first time that antifungal activity was exhibited by Aplysianin E (AKE), an antineoplastic and antibacterial glycoprotein purified from the eggs of Aplysia kurodai. AKE completely suppressed growth of the yeast form fungi, Saccharomyces cerevisiae A 5 8 1 A, Schizosaccharomyces pombe JY 1 and Candida albicans ATCC 36232 at a concentration of over 16 micrograms/mL. The colony-forming abilities of the fungi were also significantly decreased after contact with AKE. These results indicate that AKE has an antifungal property and that its mode of action is fungicidal.