A chitinase producing Bacillus subtilis CHU26 was isolated from Taiwan potato field. This strain exhibited a strong extra-cellular chitinase activity on the colloidal chitin containing agar plate, and showed a potential inhibit activity against phytopathogen, Rhizoctonia solani. The gene encoding chitinase (chi18) was cloned from the constructed B. subtilis CHU26 genomic DNA library. The chi18 consisted of an open reading frame of 1791 nucleotides and encodes 595 amino acids with a deduced molecular weight of 64kDa, next to a promoter region containing a 9 base pair direct repeat sequence (ATTGATGAA). The deduced amino acid sequence of the chitinase from Bacillus subtilis CHU26 exhibits 62% and 81% similarity to those from B. circulans WL-12 and B. licheniformis, respectively. Subcloned chi18 into vector pGEM3Z and pYEP352 to construct recombinant plasmid pGCHI18 and pYCHI18, respectively, chitinase activity could be observed on the colloidal chitin agar plate from recombinant plasmid containing Escherichia coli transformant. Cell-free culture broth of pYCHI18 containing E. coli transformant decreased R. solani pathogenic activity more than 90% in the antagonistic test on the radish seedlings (Raphanus sativus Linn.).