A novel approach to the surface modification of medical poly(vinyl chloride) (PVC) with atomic oxygen radical anions-dissolved solution (named as O- water) has been investigated. The O- water was generated by bubbling of the O- (atomic oxygen radical anion) flux into the deionized water. The surface hydrophilicities of the PVC films were investigated by contact angle measurements before and after the O-water treatment. Surface chemical compositions of the original and treated PVC films were studied Using X-ray photoelectron spectroscopy (XPS). The influence of the O- water on the Surface roughness as well as morphological alterations of the PVC films was investigated by atomic force microscopy (AFM) measurements. Results show that the O-water treatment caused an obvious increase in the surface hydrophilicity and surface energy and also caused an alteration Of the surface chemical composition, with an increase in surface roughness because of the etching effect. The modifications are attributed to the formation of oxygen-containing functional groups (C-O, C=O, O-C=O, etc.) and dechlorination, mainly caused by the reactions between the molecules on PVC surfaces and the active oxygen species in the O-water. Present method, potentially, may be applied to the Surface modification of polymers and other heat-sensitive materials. (C) 2008 Wiley Periodicals, Inc.