A gene encoding chitinase from Aeromonas sp. no. 10S-24 was cloned into Escherichia coli DH5 alpha using pUC19 and its nucleotide sequence was determined. The pCA8 ORF (open reading frame) consisted of 1482 bp encoding 494 amino acid residues. The molecular weight of the unprocessed protein was calculated to be 51,441. The pCA8 ORF is a modular enzyme composed of a signal sequence, chitin binding domains, Pro and/or Thr-rich domains, and a family 18 catalytic domain responsible for chitinase activity. The amino acid sequence of pCA8 ORF shares sequence homology with chitinase II (30%) from Aeromonas sp. no. 10S-24, and chitinase (22.9%) from Saccharopolyspora erythraea. Since no chitinase corresponding to the pCA8 ORF has been found in Aeromonas sp. no. 10S-24 culture supernatants, the gene may be silent in this strain.