The antifouling properties and biocompatibility of poly(acrylonitrile-co-maleic acid) (PANCMA) membranes were effectively improved by the immobilization of poly(ethylene glycols) (PEG) through the esterification reaction on the membrane surfaces. Chemical and morphological changes as well as biocompatibility of the original and modified membranes were characterized by Fourier transform infrared spectroscopy, elemental analysis, scanning electron microscopy, water contact angle, platelet adhesion, and cell adhesion. Permeation behaviors of the membranes were investigated by water and bovine serum albumin filtration experiments. It was found that the immobilization density of PEG, which was mainly determined by the content of reactive carboxyl groups in PANCMA copolymer, had a great influence on the performances of the studied membranes. With the increase of carboxyl group content in PANCMA copolymer, the hydrophilicity and biocompatibility of both PANCMA and PANCMA-g-PEG membranes were improved, and the latter membranes showed much better properties than the corresponding former ones. Furthermore, both the flux recovery by water cleaning and the flux recovery by chemical cleaning for PANCMA-g-PEG membrane were almost two times of those for original PANCMA membrane. It revealed that the antifouling properties of PANCMA membrane were enhanced obviously by the immobilization of PEG on membrane surface. (C) 2004 Elsevier B.V. All rights reserved.