Porous structure and permeability were studied of a composite affinity membrane contg. a functional polymeric layer for receptor binding. A polyglycidylmethacrylate layer contg. epoxy groups was formed by photoinitiated grafting. Porosity and water permeability were decreased only marginally. Bovine serum albumin, recombinant protein A (rPA), and streptavidin were immobilized independently of pH (pH 3-10). Igs of the class G were isolated from human plasma by rPA membranes in high purity. The binding capacity for Ig was 220 mg/cm2.