Gear mechanism (10), in particular for adjusting moveable parts in a motor vehicle, comprising a spur wheel (14) which is provided with external teeth (16) and meshes with an internal gear (18) that is provided with internal teeth (20), wherein the number of internal teeth (20) to generate a certain gear step-up ratio is greater by at least one than the number of external teeth (16) and the spur wheel (14) and the internal gear (18) perform an eccentric movement relative to one another, wherein the eccentric movement is directed exclusively by means of the matching tooth geometry of the internal and external teeth (20, 16).