Membranes of acrylonitrile copolymer and polyamide were modified by radiation grafting of 2-acrylamido-2-methylpropanesulphonic acid and 2-dimethylaminoethyl methacrylate. The effect of irradiation dose (from an electron beam accelerator) and method of introduction of ferrous ions on the grafting degree was studied. The sulpho- and quaternary amino groups introduced into the membranes were determined quantitatively by potentiometric titration. The grafting degree and hydrophilicity of the modified membranes were studied. Glucose oxidase was immobilized onto modified membranes, and its basic characteristics were determined : bound protein, relative activity, pH(opt), and T-opt, pH, and thermal stability, as well as storage of activity.