(-)-Sclerotiorin, isolated and purified from the fermented broth of an unidentified marine fungus (98F134), inhibited the maturation of starfish oocytes induced by 1-methyl adenine with an IC50 value of 0.50 microM. (-)-Sclerotiorin also showed antifungal activity against Saccharomyces cerevisiae, Aspergilus fumigatus, Alternaria longipes, Piricularia oryzae, Verticillium albo-atrum, Fusarium culmorum, and F. nivale with IC50 values less than 20 microg/mL.