We have developed various control algorithms to improve drivability for a 4 wheel steering vehicle, especially when towing a trailer. For improving vehicle stability at high speed, a control method that utilizes model matching method and H-infinity control, was proposed, and its effectiveness was verified. For rear edge swing-out concern in out-phase rear steering mode at low speed, a control algorithm that internally calculates the front edge trajectory and steers the rear tires without swing-out from the trajectory, was designed and experimentally verified. For reverse driving when trailer towing, we proposed a control method that makes the system stable to improve drivability. (C) 2003 Society of Automotive Engineers of Japan, Inc. and Elsevier B.V. All rights reserved.