We present a comparative study of ChiA, ChiB, and ChiC, the three family 18 chitinases produced bySerratia marcescens. All three enzymes eventu-ally converted chitin to N-acetylglucosamine dimers (GlcNAc2) and a minor fraction of monomers. ChiC differed from ChiA and ChiB in that it initially produced longer oligosaccharides from chitin and had lower activ-ity towards an oligomeric substrate, GlcNAc6.