Highly deproteinised natural rubber(HDPNR) latex was prepared by incubation of commercial high ammonia latex with a proteolytic enzyme in the presence of a surfactant, followed by repeated centrigugation for two times. The nitrogen content of HDPNR was less than 0,.02;, suggesting the nearly complete removal of protein from the rubber. A graft copolymer of natural rubber with styrene was made from HDPNR latex using trtbutyl hydroperoxie/tetraethylenepentamine (TBHPO-TEPA) as an organic redoex initiator.The styrene content, grafting efficiency and molecular weight of grafted polystyrene were significantly increased by deproteinisation. The number of grafting sites for grafting sites for graft copolymer from HDPNR latex was about three times larger than that determined for graft copolymer from untreated natural rubber latex. The difference between the behaviour of HDPNR and untreated natural rubber was due to the removal of protein and of naturally occurring antioxidants present in untreated natural rubber latex.