Abstract: A coaxial heating cable comprising a central electrically conductive heating core is formed from a conductor having a resistance with a positive temperature coefficient of at least 30% at 20.degree. C. An electrically insulating polytetrafluoroethylene sheath surrounds the core, and an outer electrically conductive ground shield encloses the sheath. The ground shield comprises a number of contiguous strands which are helically wound in a single layer around the sheath. The cable preferably has a maximum diameter of 1 mm and the conductive core conveniently has a resistivity of between 0.4 ohmsm.sup.-1 and 2 ohmsm.sup.-1. The heating cable may be used in under-carpet heating. The invention extends to a method of forming a coaxial heating cable.