The graft copolymerization of glycidyl methacrylate (GMA) onto nylon-6-membrane using benzophenone (BP) as an initiator was carried out in an alcoholic aqueous solution. The acrylic double bond of GMA participated in the grafting onto the nylon-6-membrane backbone with the epoxy groups remaining unaffected. At the end of the grafting reaction, urease was immobilized onto the modified membrane. BP concentration, GMA concentration and organic solvent seperation were studied by determining the grafting percentage. The influence of urease concentration on the immobilization efficiency was also studied. With keeping other conditions constant, the optimum conditions were shown as following [BP]: 5 x 10(-2) mM; [GMA]: 10 M; [urease]: 10 mg/ml, organic solvent: methanol. (c) 2006 Published by Elsevier Ltd.