A　chitinase　was　isolated　from　peanut　(Arachis　hypogaea　L.)　seeds.　The　procedure　entailed　extraction,　ammonium　sulfate　precipitation,　affinity　chromatography　on　Affi-gel　blue　gel,　and　high-performance　liquid　chromatography　on　POROS　20　HQ.　There　was　a　133-fold　increase　in　specific　activity　of　purified　chitinase　compared　with　that　of　the　crude　extract.　The　protein　exhibited　a　molecular　mass　of　34.4　kDa　in　sodium　dodecyl　sulfate-polyacrylamide　gel　electrophoresis　both　under　reducing　and　nonreducing　conditions,　indicating　that　it　is　a　monomeric　protein.　The　isoelectric　point　was　5.1　by　isoelectric　focusing　electrophoresis.　Optimal　pH　activity　was　5.4　and　optimal　temperature　was　40-50C.　The　enzyme　was　stable　below　55C,　but　was　rapidly　inactivated　when　incubated　at　temperatures　above　60C.　These　results　demonstrated　that　the　purified　protein　was　a　kind　of　relatively　thermostable　chitinase　from　the　peanut　seeds.