Brake system, comprising: - an actuating device, in particular a brake pedal, - a first piston-cylinder unit with a first piston and a second piston, for supplying pressure medium via a valve device to at least a first brake circuit and at least a second brake circuit, wherein the first piston can be actuated by means of the actuating device, and wherein the first piston-cylinder unit has a first pressure chamber or a first working chamber in which the first piston is arranged and to which at least the second brake circuit is connected, and wherein the first piston-cylinder unit has a second pressure chamber or a second working chamber, to which at least the first brake circuit is connected, - a second piston-cylinder unit with an electromotive drive, a transmission and at least one piston for supplying pressure medium to at least one of the brake circuits via a valve device, - a motor-pump unit, with valve device (ABS/ESP unit), to supply pressure medium to the brake circuits, - a hydraulic travel simulator is connected to a pressure chamber or a working chamber of the first piston-cylinder unit characterized in that - the pressure chamber or working chamber of the second piston-cylinder unit is connected to the first brake circuit through a hydraulic line and the second brake circuit is supplied with pressure through the first piston, wherein the second piston-cylinder unit is arranged parallel to the axis of the first piston-cylinder unit and - wherein the second piston cylinder unit is effective in a determined pressure region and that in a further, higher pressure region the motor-pump unit (ABS/ESP-unit) is used to generate pressure. - an actuating device, in particular a brake pedal, - a first piston-cylinder unit with a first piston and a second piston, for supplying pressure medium via a valve device to at least a first brake circuit and at least a second brake circuit, wherein the first piston can be actuated by means of the actuating device, and wherein the first piston-cylinder unit has a first pressure chamber or a first working chamber in which the first piston is arranged and to which at least the second brake circuit is connected, and wherein the first piston-cylinder unit has a second pressure chamber or a second working chamber, to which at least the first brake circuit is connected, - a second piston-cylinder unit with an electromotive drive, a transmission and at least one piston for supplying pressure medium to at least one of the brake circuits via a valve device, - a motor-pump unit, with valve device (ABS/ESP unit), to supply pressure medium to the brake circuits, - a hydraulic travel simulator is connected to a pressure chamber or a working chamber of the first piston-cylinder unit characterized in that - the pressure chamber or working chamber of the second piston-cylinder unit is connected to the first brake circuit through a hydraulic line and the second brake circuit is supplied with pressure through the first piston, wherein the second piston-cylinder unit is arranged parallel to the axis of the first piston-cylinder unit and - wherein the second piston cylinder unit is effective in a determined pressure region and that in a further, higher pressure region the motor-pump unit (ABS/ESP-unit) is used to generate pressure.