The purpose of this study is to develop a reliable method of functionalizing poly(ethylene terephthalate) with bioactive polymers to produce a "biointegrable" artificial anterior cruciate ligament. Radical graft polymerization of the sodium salt of styrene sulfonate (NaSS) onto poly(ethylene terephthalate) (PET) films was performed using the "grafting from" technique. Prior to the grafting, the surfaces of poly(ethylene terephthalate) films were activated by ozonation to generate peroxide and hydroperoxide reactive species on the PET film surfaces. The radical polymerization of NaSS was initiated by thermal decomposition of the hydroperoxides. The grafted PET surfaces were characterized by a toluidin blue colorimetric method, X-ray photoelectron spectroscopy, contact angle measurements, and atomic force microscopy. The influence of ozonation time, monomer concentration, and temperature on NaSS grafting ratios was examined. A total of 30 min of ozonation followed by grafting from a 15% NaSS solution at 70 degrees C for 90 min or more resulted in attachment of poly(NaSS) chains to the PET film surfaces.