In an adjustment device for adjusting the phase position of a camshaft relative to a crankshaft of an internal combustion engine which includes a hydraulic system for supplying hydraulic fluid under pressure to the adjustment device for the controlled admission to, and release thereof from, operating chambers of the adjustment device under the control of a control device including a control valve, the operating chambers are in communication with one another via control valves to permit flow of hydraulic fluid from one set of operating chambers to another by the varying torques effective on the camshaft or by controlling fluid supply to the operating chambers from the hydraulic fluid supply system.