A brake-fluid reflux type anti-skid brake control system for an automotive vehicle, comprises a main brake-fluid line fluidly disposed between a master cylinder and a wheel cylinder for supplying a brake fluid from the master cylinder to the wheel cylinder during usual braking, a brake-fluid reflux line arranged in parallel with the main line for returning the brake fluid from the wheel cylinder to the master cylinder side during operation of the system, directional control valves arranged for controlling the respective fluid flow in the main brake-fluid line and in the reflux line, depending upon a skidding condition of a vehicle wheel, and a plunger type control valve arranged between the outlet port of the master cylinder and an upstream junction of the main line and the reflux line. The control valve is responsive to a fluid pressure representing whether the anti-skid brake control system is in an operative state or in an inoperative state, in a manner so as to provide a constricted brake-fluid flow therethrough to the wheel cylinder in the operative state of the system and to provide a full brake-fluid flow therethrough to the wheel cylinder in the inoperative state of the system.