A novel single-chained antifungal protein with a molecular weight of 13 kDa displaying an N-terminal sequence with marked similarity to embryo-abundant protein from the white spruce was isolated from the seeds of Ginkgo biloba using ion exchange chromatography on DEAE-cellulose, affinity chromatography on Affi-gel blue gel, ion exchange chromatography on SP-Sepharose, and then gel filtration on Superdex 75. The protein, designated ginkbilobin, exerted potent antifungal activity against a variety of fungi, including Botrytis cinerea, Mycosphaerella arachidicola, Fusarium oxysporum, Rhizoctonia solani, and Coprinus comatus. Ginkbilobin exhibited a moderate antibacterial action against Staphylococcus aureus, Pseudomonas aeruginosa, and Escherichia coli. It suppressed the activity of HIV-1 reverse transcriptase and the proliferation of murine splenocytes.