In order to improve blood compatibility, the surfaces of poly(vinyl chloride) (PVC) were treated using irradiation with ultraviolet light, O-butyrylchitosan (OBCS) being coated on the film surface to photolyze azide groups, thus crosslinking OBCS and PVC together. Surface properties of PVC were investigated by attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), electron spectroscopy for chemical analysis (ESCA) and the water contact angle measurements. The blood compatibility of PVC was evaluated by platelet rich plasma (PRP) contacting experiments and the results were observed by scanning electron microscopy (SEM). It demonstrated that fewer platelets adhered to the OBCS grafted surfaces than to the blank PVC. The modifications could be carried out to tailor PVC biomaterial to meet the specific needs of different biomedical applications. These results suggest that the photocrosslinkable chitosan developed here has the potential of serving as a new biomaterial in medical use. (C) 2003 Elsevier Ltd. All rights reserved.