The catalase (from Aspergillus niger) has been immobilized by a chemical method on the pous SiO2 modified with gamma-aminopropyltrietoxysilane, followed with glutaraldehyde and by a physical method in alginate and gamma-carrageenan gel. Optimum support:enzyme ratios and pH values were determined for modified SiO2 in a series of immobilization reactions of catalase in the presence of the crosslinking agent glutaraldehyde, and for alginate and gamma-carrageenan in the presence of hemoglobin and bovine serum albimine, pH and temperature-dependent activity variations and the stability properties of immobilized catalase preparations were investigated. Rate constants for H2O2 decomposition and catalase deactivation were determined. The decomposition rate of H2O2 used in the cold pasteurizatioan of milk were investigated in a discontinuous batch type reactor system. Activity half-lives of immobilized catalase were determined.