A length of filament, such as wire or optical fibre, is loosely coiled on a flat carrier, in the form of a figure of eight the lobes of which are laid respectively in clockwise and anti- clockwise directions. The coil is formed by feeding the filament (41) downwards on to the carrier through a guiding arrangement which causes the downward path ofthefilament to rotate alternately in clockwise and anticlockwise directions. The guiding arrangement may be a figure of eight shaped double ring structure, with further guide members within the rings, or a gimbal-mounted guide member (42) which is oscillated, by two sets of reciprocating means (65, 66), about two horizontal axes at right angles to one another.