A novel antifungal protein, designated chrysancorin, was isolated from seeds of Chrysanthemum coronarium var. spatiosum with a procedure involving ion exchange chromatography on DEAE-cellulose, affinity chromatography on Affi-gel blue resin, ion exchange chromatography on SP-Sepharose and FPLC-gel filtration on Superdex 75. The N-terminus of chrysancorin displays sequence similarity to the genomic sequence of chromosome 1 from Arabidopsis thaliana BAC T19E23. Chrysancorin exhibits a molecular mass of 13.4 kDa in gel filtration and SDS-polyacrylamide gel electrophoresis. It stimulates the proliferation of mouse splenocytes and inhibits the activity of human immunodeficiency virus-1 reverse transcriptase. The protein possesses antifungal activity against Botrytis cinerea, Mycosphaerella arachidicola and Physalospora piricola, but not against Rhizoctonia solani, Fusarium oxysporum and Coprinus comatus. However, we could not detect antibacterial activity against a variety of bacteria.