In a traction slip-controlled brake system for automotive vehicles, comprising an auxiliary pressure source and a pedal-operated brake valve through which pressure fluid from the auxiliary pressure source can be applied to the wheel brakes. A first valve switchable from a locking position into a passage position is switched into a pressure fluid conduit leading from the auxiliary pressure source to the wheel brakes of the one motor vehicle axle, and a second valve is switched into the brake conduit connecting the wheel brakes of the said motor vehicle axle to the brake valve. The said second valve can switch over from a passage position into a locking position. Moreover, a check valve is provided in the line section connecting the first valve to the wheel brakes of the one motor vehicle axle, with the said check valve precluding a flow back of pressure from the wheel brakes to the first valve. An additional third valve is provided in a line connecting this line branch to the return line which valve, in non-excited condition, for safety reasons, will then open the communication with the pressure fluid reservoir.