The liquid-phase graft reaction of hydroquinone (HQ) was carried out onto the surface of medical-grade polypropylene (PP) films with the photosensitizer, benzophenone (BP). The effects of various reaction conditions on the graft yield of the samples and the changes in physicochemical properties of the surface of the samples were determined by FTIR/FMIR and surface tension measurements. As BP concentration was increased, the graft yield increased up to a maximum at 2.5 wt % of BP and then decreased. Graft yield was increased with irradiation time and HQ concentration before leveling at 3.5 wt %, in 150 min. The surface tension of samples were increased with the increase of graft yield up to 37 dyn/cm.