Graft copolymerization of methacrylic acid (MAA) or acrylamide (AM) from an aqueous solution onto acrylonitrile-butadiene-styrene terpolymer (ABS) was initiated by the thermal decomposition of polymeric hydroperoxides, which are formed upon UV irradiation of ABS, which contains anthracene. Diffusion of anthracene at room temperature from a methanolic solution into ABS was affected by the acrylonitrile content of ABS. The graft yield was independent on the concentration of anthracene in the wide range of 0.03 X 10(-3) to 14.29 X 10(-3) mol/L in ABS. The graft polymerization reaction does not occur below 100 degrees C. The effect of other variables, such as time of irradiation, intensity of UV, reaction time, and concentration of monomer in aqueous solution, on the amount of monomer grafted to ABS were also investigated. The contact angle significantly decreases upon grafting, indicating that the graft layer is on the surface of the polymer.