Anti-lock brake system (ABS) prevents vehicular wheels from locking by ensuring tire slip ratio within a certain range while braking on slippery road surfaces. In the design of ABS controller, an inherent nonlinearity in a braking mechanism should be taken into account to increase robustness against uncertainty in vehicle dynamics which is substantially changed by road surface conditions, vehicle mass and other factors. In the case of large commercial vehicles, the brake actuators are sluggish in response which make it difficult to design an ABS controller having good performance. To deal with the nonlinearity, the methodology of sliding mode control is used. A new method to use sluggish actuators with sliding mode controller is proposed.