Abstract: A power assisted hydraulic steering device in which the hydraulic actuators and the control valves are all contained in a common cylindrical housing surrounding a control shaft connectable to the steerable wheels of the vehicle, the actuator comprises an annular piston formed on the control shaft and housed in a cylinder defined between the control shaft and the sleeve. A control rod linked to the steering column is housed within the control shaft, which is hollow, and carries a valve element which cooperates with interior parts of the hollow control shaft to control fluid pressure applied to one side of the annular piston to cause displacement in one direction, or both sides of the annular piston, which has different areas on opposite sides, to cause displacement in the opposite direction.