Abstract: In a stair-climbing vehicle for negotiating steps, ledges and stairs comprising a vehicle body having wheel support arms mounted thereon at opposite sides and in spaced relationship so as to be pivotable about a wheel support arm shaft and wheels rotatably mounted on the free ends of the wheel support arms, climbing arms are supported on the vehicle pivotable about the pivot axes of the support arms. The climbing arms are linearly extendable for moving the wheels from one step to the next, one wheel, one wheel support arm and one climbing arm forming together a stair climbing module.