Catalase was immobilized on the chitosan film that is a natural polymer. Studies were done on free catalase and immobilized catalase on chitosan film concerning the determination of optimum temperature, optimum pH, thermal stability, storage stability, operational stability, and kinetic parameters. It was determined that optimum temperature for free catalase and immobilized catalase on chitosan film is 25 degrees C, and optimum pH is 7.0. It was found as K-m = 25.16 mM, V-max = 24042 mu mole/min mg protein for free catalase, K-m = 27.67 mM, V-max = 1022 mu mole/min mg protein for immobilized catalase on chitosan. It was observed that there was a big difference between V-max value of the free catalase and V-max value of immobilized catalase on chitosan film whereas there were minor changes in the value of K-m for free catalase and immobilized catalase. It was found that storage stability at 5 degrees C for immobilized catalase stored wet is greater than free catalase and immobilized catalase stored dry, and immobilized catalase showed a operational stability. (C) 2000 Elsevier Science Inc. All rights reserved.