Abstract: The invention relates to a hydraulic drive system comprising a plurality of hydraulically driven piston units with cam rollers, which are disposed to act against a wave-shaped cam profile of a cam curve element, so that linear movement of the cam rollers against the cam profile produces a relative driving movement between the cam element and the piston units. The characterizing feature of the invention is that the drive system is composed of separate, assembled cam curve element modules and separate assembled piston units.