Various polymer surfaces--polyethylene, polypropylene, polystyrene, polyethylene terephthalate and poly(methyl methacrylate)--were modified by water vapour plasma discharge treatment. The plasma-treated polymer surfaces were characterized by water contact angle measurement and electron spectroscopy for chemical analysis. It was observed that by the water vapour plasma treatment, the wettability of the polymer surfaces increases largely and almost all functional groups produced on the surfaces are hydroxyl groups. The interactions of Chinese hamster ovary cells with the polymer surfaces having hydroxyl groups by plasma treatment were investigated. The cells adhered and grown on the polymer surfaces were counted using a haemocytometer and photographed with an inverted microscope with a camera attached. The water vapour plasma-treated polymers showed good adhesion, spreading and growth properties on the surfaces with high hydroxyl group density. We confirmed that the water vapour plasma treatment is a simple and effective method to produce hydroxyl groups on the polymer surfaces, which probably have a positive effect on cell adherence.