In a brake system for motor vehicles, having a master brake cylinder (4) which can be actuated by means of a brake pedal (19) and to which wheel brakes (6, 7, 8, 9) are connected, having an electrically controllable pressure generating device (2), having a pressure regulating valve arrangement (5) for regulating and/or controlling a wheel brake pressure induced at a wheel brake (6, 7, 8, 9), and having a first electronic control and regulating unit (10) which controls or regulates the pressure generating device (2) and/or the pressure regulating valve arrangement (5), it is sought to a provide brake force assistance means which is independent of the functioning of the pressure generating device. For this purpose, said brake system comprises an electrically controllable auxiliary pressure generating device (60) by means of which the master brake cylinder (4) can be actuated, in particular by means of which a pressure in an intermediate chamber (61) of the master brake cylinder (4) can be controlled or regulated.