The subject invention discloses a thermoplastic composition which is comprised of a blend of a thermoplastic resin and an elastomer, wherein said thermoplastic resin is selected from the group consisting of polyphenylene ether and polystyrene, wherein said elastomer is comprised of a conjugated diene selected from 1,3-butadiene and isoprene, wherein said elastomer is highly branched, wherein said elastomer is characterized by having a G' and G'' frequency crossover of no more than 4 radians/s at 100.degree. C., wherein the thermoplastic resin is present in an amount which is within the range of about 5 parts by weight to about 95 parts by weight, and wherein the elastomer is present in an amount which is within the range of about 5 parts by weight to about 95 parts by weight, based upon the total weight of the thermoplastic composition.