In a power-operated chuck (1) with clamping jaws (3) that are guided so they can move radially within a chuck body (2) and are in a drivable connection via intermediate elements with a clamping piston (4) upon which a hydraulic fluid can act in one or both directions and which is inserted in the chuck body (2) in such a way that it can move axially, a pressure sensor (41) installed in the chuck body (2) is provided in order to monitor the hydraulic fluid pressure existing in the pressure chambers (7 and 8) assigned to the clamping piston (4), the pressure sensor (41) being connected to one or both pressure chambers (7, 8) via hydraulic fluid channels (42, 43). Furthermore, the pressure sensor (41) has a receiver assigned to it which is connected to a unit (45) for evaluating the signals received from the pressure sensor (41). This embodiment makes it possible for the pressure existing in a pressure chamber (7 or 8) to be continuously detected both when it is being charged and during operation and for this information to be used in order to control a machine tool.