Abstract Extracellular chitinase was purified from the culture liquid of the marine bacterium, Bacillus sp. LJ-25 , and its enzymatic properties were examined. The purified chitinase exhibited a single band on SDS-PAGE and the molecular weight was estimated to be approximately 50 kDa. The optimum pH and temperature for the enzymatic activity were 7.0 and $35^{circ}C$, respectively. The activity of the chitinase was strongly inhibited by $Zn^{2+}$ and slightly inhibited by $Ba^{2+},{;}Co^{2+},{;}Mn^{2+},{;}and{;}Cu^{2+}$. The purified chitinase did not hydrolyze $p-nitrophenolN-acetyl-{ata}-D-glucosaminide{;}(GlcNAc)_2$ and Micrococcus lysodeikticus cells, which are known to be the substrates for exo-type chitinase. Among the hydrolyzates of colloidal chitin, $(GlcNAc)_2$ was in the highest concentration with small amounts of GlcNAc and $(GlcNAc)_3$.</TEX>.