We present a new method for heparinization on the surface of polyurethane. The segmented polyurethane was first modified with an epoxide monomer and followed by a ring-opening reaction with diethanolamine to introduce sufficient hydroxyl groups on the surface of cast film. On this film surface, a cationic monomer was grafted by using tetravalent Cerium salt as an initiator. Heparin was immobilized in high efficiency on the ionized surface through static interactions in aqueous solution. The structure of ionized and heparinized surfaces were characterized by attenuated total reflectance infrared spectroscopy (ATR-FTIR) and electron spectroscopy for chemical analysis (ESCA) spectra. The platelet-rich plasma (PRP) contacting test and the platelet-poor plasma (PPP) clotting time measurements showed that the immobilized heparin retained its strong anticoagulant property. The release of heparin from film into salt solution was also studied, and it was found that only a small portion of heparin (10-20%) was released over a period as long as 10 h. It is expected that this new method for surface heparinization can be used to prepare antithrombogenic materials with long-term stability. (C) 2000 John Wiley & Sons, Inc.