On the basis of the proposal that highly reactive vinyl acetate (VAc) radicals could facilitate the grafting of other monomers on to natural rubber (NR), the effect of the presence of small quantities of VAc on the efficiency of grafting methyl methacrylate (MMA) on NR molecules in latex form has been studied. Several VAc concentrations have been examined, and the initiator azo-bis-isobutyronitrile was added to the systems to promote the formation of VAc radicals. There is good evidence for the formation of graft copolymer under the conditions used, but it was found that the grafting is not significantly affected by the presence of VAc. It is proposed that this could be due to the fact that the oil-soluble initiator is not accessible to the relatively large amount of VAc present in the aqueous phase. A higher than expected portion of the products was extractable with petroleum ether, and this may be attributable to the initiator inducing a small amount of degradation in the rubber. Finally, although acetone is not considered a good solvent for NR, it was found to be capable of extracting from the graft copolymers relatively large quantities of material containing the cis-1,4-polyisoprene structure. This observation is consistent with the effect that PMMA grafts on the NR molecules would have on their solubility in this solvent.