A catalase preparation from a newly isolated Bacillus sp. was covalently immobilized on silanized alumina using glutaraldehyde as crosslinking agent. The effect of the coupling time of the enzyme-support reaction was determined in terms of protein recovery and immobilization yield and a certain balance point was found after which the activity recovery decreased. The activity profile of the immobilized catalase at high pH and temperature was investigated. The immobilized enzyme showed higher stabilities (214 h at pH 11, 30 degreesC) at alkaline pH than the free enzyme (10 h at pH 11, 30 degreesC), The immobilized catalase was inhibited by anionic stabilizers os surfactants added to the hydrogen peroxide substrate solution.