The kinetics of graft copolymerization of polyacrylonitrile (PAN) onto polyester (PET) and the simultaneous homopolymerization initiated by the potassium penoxomonosulfate (PMS)-ascorbic acid (H(2)A) redox system were studied separately. Results on the graft copolymerization was adequately explained by a mechanism which also accounts for the reason for simultaneous homopolymerization. The observed homopolymerization results agreed with the proposal. Kinetic chain-length measurements on the graft copolymer and homopolymerization were used to evaluate the kinetic parameters.