Abstract: Novel elastomer/oxymethylene polymer blends are disclosed whose impact strength or resistance has been enhanced, with no appreciable diminution in their outer useful properties, by the inclusion therein of a novel elastomer/oxymethylene graft copolymer compatibilizing agent prepared by grafting polyformaldehyde or oxymethylene copolymer chains onto a halogenated elastomeric polymer by means of a reaction initiated at graft sites, i.e., at the sites of the haloelastomer's halo substituents, using, e.g., an initiated site-forming cationic salt.