A method of removing a metallic cable core that extends through an outer cable sheath of a length of data transmission cable is disclosed. The core is surrounded by a filler material contained within the outer cable sheath as an integral part of the cable. The method comprises the steps of resistively heating the core by supplying electric current to it to reduce the viscosity of the surrounding polymer material; and pulling the core out of one end of the outer cable sheath while the viscosity of the filler material is in a reduced state.