Abstract: A patient positioning support for an operating theatre table (2) has a saddle (18) for clamping to the rail (8) which runs alongside the edge of the table and a pair of articulating arms (26, 32) attached to the saddle for holding a pad in contact with a patients body or limb. The devices are mounted in pairs and are lockable in positions which overlie the tame or lie outboard of the table or below the table when not required. The locking action is by friction but radial arrays of teeth (66, 68), which are locked by hand screws (62), give the preferred locking action. Other items of equipment such as arm boards, neural head supports and stirrups can be substituted for the pad.