Immobilization of the enzyme catalase on natural and modified montmorillanit analsim-clays was investigated using a batch system. Such an immobilization does not result in enzyme inactivation and constitutes a valuable method for immobilizing catalase at high ionic strength. In the immobilization process, the effect of pH, ionic strength and reaction temperature were chosen as parameters. Furthermore the optimization of immobilization conditions were studied using data obtained from experimental results. For the free catalase and three different immobilized catalase enzymes, the optimum pH values 8, 7, 7 and 8; reaction temperature 30 degrees C; ionic strength 0.25 M were found. It was determined that enzyme activity for enzyme supported by natural clay was 73.3%, when it was retained during the storage at 4 degrees C for a period of 60 days. It was observed that storage and operational stabilities of the enzyme increased with immobilization. The results obtained show that montmorillanit analsim-clay is valuable and favourable support the simple adsorption of enzymes.