Abstract: A pneumatic piston-cylinder unit has a cylinder (1) in which an air piston (4) with a tubular piston rod (5) is reciprocably actuated by compressed air from two main air channels (18, 19). The air cylinder (1) includes an integrated hydraulic control system (6) having an actuation device (8) which is fixedly mounted in the air cylinder (1) for creating a flow of hydraulic fluid through hydraulic control system (6) when compressed air is present in the main air channels (18, 19) and for stopping the flow of hydraulic fluid and thereby preventing the air piston from moving when there is no compressed air in the main channels (18, 19). A piston (34) and a cylinder (28) of the hydraulic control system (6) are displaceable an adjustably long distance in relation to each other to make it possible to open and close, respectively, a larger or smaller hydraulic fluid passageway thereby controlling the moving speed of the air piston (4) while maintaining the air pressure.