This article concerns the nonlinear tracking control of trailer systems that consist of a steering tractor and a passive trailer, linked together with rigid joint and having nonholonomic velocity constraints. We propose a globally asymptotically stable (GAS) tracking control law using the Lyapunov direct method. The GAS tracking control law is completed by considering the posture term of the trailer systems. We selected two types of trailer systems for examples: the two-wheeled trailer system and the car-like trailer system. The simulation results represent the effectiveness of our proposed method. In addition, there is a plan to test the path following ability of the trailer system. (C) 1999 John Wiley & Sons, Inc.