(57) Electrical insulation comprises (1) an inner layer of a cross-linked polymer, e.g. an ethylene/tetrafluoroethylene copolymer, an ethylene/chlorotrifluoroethylene polymer or a vinylidene fluoride polymer, and (2) an outer layer of an aromatic polymer having a glass transition temperature of at least 100°C, e.g. a polyether ether ketone, a polyether ketone or a polyether sulfone. Such insulation combines excellent properties under normal service conditions with low smoke evolution on burning, and is therefore particularly useful for aircraft wire and cable.