Radiation-induced graft copolymerization of 4-vinyl pyridine (4-VP) and its binary mixture with acrylonitrile (AN) onto isotactic polypropylene has been studied in aqueous medium. Percentage of grafting has been studied as a function of different reaction parameters and the optimum conditions for affording maximum percentage of grafting have been evaluated. It was observed that there exists an optimum composition of the binary mixture at which percentage of grafting is maximum. The maximum percentage of grafting is obtained at the total monomer concentration of [AN + 4VP] = 0.009 moles. The graft copolymers were characterized by IR spectroscopic methods. An attempt has been made to discuss the effect of acceptor monomer (AN) on percentage of grafting of donor monomer (4-VP).