Quaterpolymers are described which are composed of the following copolymerized monomer units (in mole %):(a) 55 to 30% of tetrafluoroethylene, (b) 60 to 40% of ethylene, (c) 10 to 1.5% of hexafluoropropylene and (d) 2.5 to 0.05% of a vinyl monomer which has "bulky" side chains and which can be, for example, a perfluorinated olefin, a perfluorinated vinyl ether, a perfluoroalkyl-substituted vinyl compound, a vinyl or allyl ether or an allyl or vinyl ester. The tensile strength and, in particular, the elongation at break at elevated temperatures is improved by the incorporation of both hexafluoropropylene and "bulky" vinyl monomers. The quaterpolymers are suitable for the manufacture of extruded articles, monofilaments and wire-coatings.