Polyethylene (PE) film surface is modified by combining plasma treatment and soluble eggshell membrane protein (SEP) immobilization. Contact angle measurements, attenuated total reflectance infrared spectroscopy, and X-ray photoelectron spectroscopy confirm that SEP adheres tightly to the PE film surface. Mouse 3T3 fibroblasts are used as model cells to evaluate the biocompatibility of PE film surfaces before and after modification. Plasma pretreatment can incorporate polar groups onto the surface, benefitting tight immobilization of SEP. The hydrophilicity of the PE film surface modified by combining plasma treatment and SEP immobilization is increased as evidenced by contact angle measurements, and the biocompatibility of the surface is greatly improved as shown by cell culture. The surface of the modified material can endure rinsing with 10% acetic acid (a good solvent of SEP), which would be an advantage for further application as a biomaterial. (c) 2005 Wiley Periodicals, Inc.