A method of attaching terminals to the wires of a cable having a plurality of wires all insulated from one another with separate insulating layers is disclosed, wherein the wires are surrounded, in the region where a terminal is to be connected, by a liquid conductive material. After the outer cover of the cable has been removed (if it has one), a terminal element is positioned in contact with the liquid conductive material adjacent the wires of the cable at the said region. A rising voltage is then applied between the terminal and one end of the wire which is to be connected to the terminal. The voltage continues to rise until the occurrence of dielectric breakdown of the insulation surrounding the wire to be connected allowing a spark to jump from the wire to the terminal and to burn a hole through the insulating layer allowing the liquid conductive material to flow in and make contact with the wire. Subsequent solidification of the liquid conductive material makes the connection permanent.