A filling composition for filling the interstices between the strands of a multi-stranded conductor of an electrical cable, comprises a polymeric compound which has a 100 gram needle penetration value at 25 DEG C of from 50 to 100 tenths of a millimetre, and particles of a water-swellable material having a particle size of not more than 200 microns. The components of the composition may be used together, that is in admixture, or separately. In the latter case the interstices are filled with the polymeric component and the surfaces of the latter are dusted or coated with the particulate water-swellable component.