A step climbing attachment suitable for attachment to a wheeled chair is described. The step climbing attachment includes a chassis for mounting one or more ground engaging units, a first and a second ground engaging unit mounted to the chassis, at least one of the first and second ground engaging units adapted to move relative to the other of the first or second ground engaging units and the chassis, the relative movement being between a ground engaging position and a step-engaging support position so that in use at least one of the first and/or second ground engaging units engages a step.