Abstract: An actuating cylinder (2), especially for a hydraulic clutch operation device in a motor vehicle, is disclosed, having a piston unit (6) arranged in a housing (4) and guided via a guide sleeve (8) which is permanently connected to the housing, wherein the piston unit can be displaced by means of a thrust bolt (10). A thrust bolt head (12) is permanently attached directly to the thrust bolt and its relative position with regard to the thrust bolt determines the working stroke (H) of the piston unit, which is done at the time of assembly of the actuating cylinder already. The thrust bolt head is slid onto the thrust bolt and the working stroke between the guide sleeve and the thrust bolt head is adjusted before the thrust bolt head is attached to the thrust bolt. The actuating cylinder and its assembly are simplified according to this invention, so that subsequent work in adjusting the working stroke can be eliminated.