Proposed is a brake system for motor vehicles, with a pressure-genrating device (1) to which the individual brake cylinders (12 to 15) associated with each wheel are connected by hydraulic lines. Fitted in the hydraulic lines are actuator units (8, 9) made up of a piston/cylinder assembly (16 to 19) and an actuator (20), the actuator units making it possible to shut off the hydraulic lines. In order to convert the brake system into an active brake system, the invention proposes that, when the pressure-generating device (1) and, at least one actuator unit (8, 9) are simultaneously actuated, the force resulting from the pressure build-up in the pressure-generating device (1) and the external actuating force produced by the actuator (20) are applied jointly at the piston (22, 25) of the piston/cylinder assembly (16, 17, 18, 19).