To improve the antifouling properties of a hollow fiber PES membrane it was functionalized with the zwitterionic monomers [2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl) ammonium hydroxide (MEDSAH) and 2-(methacryloyloxy) ethyl phosphorylcholine (MPC) by photografting. Each modified PES membrane (PES-g-MEDSAH and PES-g-MPC) was investigated for its antifouling properties for organic fouling and biofouling. To evaluate the organic antifouling properties, each membrane was used to filter a solution of bovine serum albumin or lysozyme. For biofouling, the antifouling properties were evaluated by immersion tests and filtration of a Pseudomonas putida solution. The modified PES membranes had better organic antifouling properties and higher biofouling resistance than the unmodified PES membrane. In the immersion test, almost no bacteria were detected on the modified membrane surfaces. Thus, surface functionalization of PES membranes with zwitterionic monomers can improve antifouling properties for organic fouling and biofouling. (C) 2012 Elsevier B. V. All rights reserved.