A chitosan degrading fungus which had been isolated in our laboratory and identified as Penicillium spinulosum by the International Mycological Institute (England), was used for the production of chitosanase in a salt medium containing Rhizopus cell walls as the sole carbon source. Although chitosanase was produced under all the conditions tested about 1 % cell wall concentration maximized enzyme production. The enzyme was purified 50 fold by using ammonium sulfate precipitation and ion-exchange chromatography and then characterized. Optimal pH and temperature values of the enzyme were determined as pH 5 and 55 degrees C, respectively. The K-m and V-max values were found as 1.7 mg chitosan/ml and 146.4 mu mol glucosamine/ml-min, respectively by using Lineweaver-Burk plot. Approximately 15% and 50% activity losses were observed during a 20 minutes heat treatment at 45 and 65 degrees C at pH 4.2, respectively.