A chitinase gene (Chi3K) was cloned from the genomic DNA of Vitis vinifera cv. Koshu. The structural gene comprised 891 bp without introns and encoded 297 amino acids. The Chi3K product showed high similarity to the class III chitinase of V vinifera cv. Pinot noir. Chi3K was expressed using a bacterial expression vector for purification and enzymatic characterization of its gene product. The recombinant chitinase exhibited hydrolytic activity toward glycol chitin and its optimum pH was 4.0. It also inhibited the growth of Botrytis cinerea, which causes grey mold disease in grapes.