An antifungal principle of defatted seed power of Cassia tora Linn. was isolated by extraction of an aqueous paste of the powder with benzene, followed by column chromatography over activated silica gel C using chloroform as the developing solvent. Besides chrysophanic acid and other hydroxyanthraquinone derivatives, the major antifungal compound was identified as chrysophanic acid-9-anthrone, the structure of which was assigned on the basis of its chemical properties and uv, ir, nmr and mass spectral analysis. The compound was active against Trichophyton rubrum, T. mentagrophytes, Microsporum canis, M. gypseum and Geotrichum candidum in broth in the presence of 100 mug/ml L-ascorbic acid as antioxidant.