The covalent immobilization of bovine liver catalase (CAT) oil to florisil via glutaraldehyde was investigated. Optimum immobilization pH and temperature were determined as pH 6.0, 10 degrees C respectively, while the amount of initial CAT per, of carrier and immobilization time was determined as 5 mg . g(-1) and 120 min, respectively. The V-max values for free and immobilized CAT were found to be 1.7 x 10(5) and 2.0 x 10(4) mu mol H2O2 . min(-1) mg protein(-1), respectively, whereas K-M values were 33.3 mM and 1722.0 mM respectively. Operational stability was determined by using a stirred batch-type column reactor. Immobilized CAT retained about 40% of its initial activity after 50 uses. It showed higher storage stability than free CAT at 4 degrees C and 25 degrees C. Its storage stability increased with increasing relative humidity (RH) from 0 to 20% of the medium. The highest storage stability was obtained in 20% RH, however, further increase in RH from 40 to 100% significantly decreased the storage stability.