A new antifungal compound, which was named pafungin, was purified form culture broth of Pseudomonas aeruginosa K-187 grown aerobically in a shellfish waste-containing medium. The molecular weight of pafungin was 66000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Pafungin＇s composition was similar to that of complex carbohydrate. Pafungin was stable at pH 5-7, and its thermal stability was 100 degrees C for 40 min. The role of purified pafungin in the suppression of Fusarium oxysporum that causes damping-off disease was studied. Suppression of swelling and lysis of the hyphae were observed in the presence of pafungin. When covalently immobilized on an enteric coating polymer (hydroxypropyl methylcellulose acetate succinate), which has reversible soluble-insoluble characteristics with pH change, the pafungin retained its antifungal activity completely. This is the first report of a high-molecular-weight nonenzymatic antifungal compound from a prokaryote.