A step-climbing attachment for a wheeled chair, the attachment including a wheel-mounting chassis for mounting wheels, a first and a second wheel each mounted on the wheel-mounting chassis for rotation about their axes, the first and second wheels are each adapted to move relative to the other, the relative movement in use being between a ground engaging position and a step-engaging position so that in use at least one of the first or second wheels engages a step, and respective link arms 128 connected to the chassis so as to mount the first wheel and the second wheel to the chassis and allow each wheel to swing from the ground engaging position to the step-engaging position. At least one of the wheels has a hub 135 and a motor 190 and gearbox mounted within the hub. The motor and gearbox are connected to the respective link arms 128 so as to pivot the other of the first or second wheels into a step engaging position.
