Abstract: A piston-cylinder unit includes a cylinder having an inner cylindrical wall face; a pressure piston slidably accommodated in the cylinder and arranged for being driven into the cylinder by an external force. The cylinder defines a cylinder chamber in which pressure is generated by the pressure piston forced into the cylinder. The pressure piston has a radial bottom and a generally cylindrical outer face extending axially away from the piston bottom. In the outer face of the pressure piston, adjacent the bottom, there is provided a circumferential recess which, together with an overlying circumferential portion of the inner cylindrical wall face of the cylinder defines an annular chamber surrounding the pressure piston. The radially measured width of the annular chamber gradually decreases in a direction axially away from the piston bottom. A sealing ring is disposed in the annular chamber and sealingly engages the inner face of the cylinder even when situated in the widest zone of the annular chamber.