Abstract: A chassis for stair-climbing wheel chairs with step wheels mounted on a star-shaped rotating supporting means, the step wheels being surrounded by an elastic endless belt, the latter being in contact with portions of the step wheel peripheries. Locking means are mounted on the rotatable supporting portion and are lockable to the inside of the belt means, when the latter is pressed towards the locking means by a stair during the stair climbing operation. When the chassis climbs, the belt being driven, the supporting means will rotate. The locking means releases when the stair has been passed.