Near u.v. light induced graft copolymerizations of water-soluble monomers such as acrylamide, acrylic acid, the sodium salt of 4-styrenesulfonic acid and N,N-dimethylaminoethyl methacrylate onto pristine and Ar plasma pretreated film surfaces of high-density polyethylene, poly(ethylene terephthalate) and polystyrene were carried out. Using angle-resolved X-ray photoelectron spectroscopy (XPS), the chemical composition and structure of each copolymer surface and interface were investigated. The XPS results show that in each case Ar plasma treatment leads to a substantial enhancement of the density of the surface graft, and, in the case where substantial grafting takes place, the grafted polymer penetrates or becomes partially submerged beneath a thin surface layer which is much richer in the substrate polymer. The resulting surface structures were further confirmed and distinguished by data obtained using dynamic water contact angle measurements.