A hydraulically controlled actuator for actuation of an exhaust-side gas exchange valve of an internal combustion engine, containing a control piston that is displaceable within a cylinder and, with piston sides facing away from one another, delimits pressure chambers, of which the one pressure chamber impinges upon the gas exchange valve in the closing direction and the other pressure chamber impinges upon the gas exchange valve in the opening direction. In the actuator is provided at least one spring element, which can be brought into a preloaded state by the control piston moving in the closing direction of the gas exchange valve, and whose stored potential energy accelerates the gas exchange valve in the opening direction at least at the beginning of an opening phase, is provided. This results in a reduction in the energy expended in the context of valve actuation.