Two forms of chitinase C (Chi-I and Chi-II) were purified until homogeneity from the culture supernatant of a transformantEscherichia coli harbouringchitinase C gene from the halophilic bacteriumSalinivibrio costicola strain 5SM-1. Chi-II was derived from Chi-I by C-terminal processing. Chi-I and Chi-II showed similar salinity optimum at 1–2% NaCl and retained more than 80% of their activity at 3–5% NaCl and more than 50% residual activity at 14% NaCl. The two enzymes could also well function (activity > 95%) in the absence of NaCl. Both had highest activity at pH 7.0 and 50 °C and both were stable over a wide range of pH (3.0–10.0). More than 50% activity remained at 80 °C after 60 min treatment. Among 4 major cations contained in sea water, only Mg2+ at 10 mM increased activity about 10%. Usingp-nitrophenyl-N,N′-diacetylchitobiose as substrate, Chi-I and Chi-II hadK m of 30 and 31.8 μM andV max of 10 and 9.2 μmol/h/mg protein, respectively. Chi-I and Chi-II were classified as exochitinases by product analysis of theE. coli culture supernatant with high performance liquid chromatography (HPLC) and thin-layer chromatography (TLC).