A direct method for the determination of the catalytic activity of immobilised enzymes by use of a miniaturised calorimeter is presented. The possibilities and advantages of the calorimetric method are demonstrated by investigations with catalase immobilised on macroporous glass membranes as model enzyme. The investigated enzyme carrier systems are characterised by a high catalytic activity, a marked long-term stability and by the possibility for the regeneration of the activity by repeated immobilisation.