An antifungal principle of the dried rhizomes of Curcuma zedoaria was extracted with hot ethanol. By successive chromatography on neutral alumina and silica gel, three antibiotic compounds A, B, and C, all active against Trichophyton rubrum, Aspergillus niger and Saccharomyces cerevisiae, were obtained in chemically pure form. By uv, ir, pmr and ms analysis, the structure of the most abundant one of these compounds (C, 69.8%; H, 6,8%; and 0.23.4%) was assigned as ethyl p-methoxycinnamate (EPMC). The proposed structure was confirmed by synthesis and comparison of the chemical and biological properties of the natural and synthetic products. EPMC inhibits the growth of Trichophyton rubrum, Aspergillus niger, Saccharomyces cerevisiae and Epidermophyton floccosum at a concentration less than 10 mug/ml; A. fumigatus, Penicillium purpurogenum, Trignoposis variabilis, Microsporum gypseum, Sclerotium rolifsii, Geotricular candiade, Fusarium oxysporum and Helminthosporium oryzale at a concentration less than 25 mug/ml; and Candida krusei and T. mentagrophytes At a concentration less than 50 mug/ml. The spores of T. rubrum Lose viability or ability to germinate when wxposed to its ethanolic solution (30 mug/ml) for 2 hours.