An electrical heating cable of the type in which two power supply conductors extend along the length of the cable and the heating element extends along the length of the cable and between the two conductors, connected in parallel between the conductors. One or both of the conductors is encased in the sheath of material which has a positive temperature coefficient and the heating element is in electrical contact with the outer surface of the sheath. As a result the sheath is electrically connected in series between each heating element and the conductor encased by the sheath. The sheath may be manufactured from a material which provides a very rapid rise in electrical resistance at a predetermined temperature, thereby enabling the manufacture of a cable which delivers substantially constant power below the predetermined temperature with a rapid reduction in power output at the predetermined temperature.