Abstract: An apparatus for operating the valves on internal combustion engines with a variable valve lift curve has a multimember, rotary gear, which comprises the valve-guiding case, a rotary cam connected to the case via a pivot joint and whose drive is derived from the crankshaft, an intermediate member operated by the cam by a curve joint and a driven member, which is supported by a joint on the case and operatively connected to the intermediate member via a joint and which transfers the movement to the valve. The intermediate member is supported by a curve joint on the case, with the curve of the curve joint, located on the intermediate member, having a portion forming a locking device and also a control portion. The position of the curve supported on the case and associated with this curve joint or the position of the pivot joint of the cam is adjustable during operation.