This paper proposes an adaptive sliding-;mode algorithm for estimating the desired yaw moment for a vehicle stability-;control system in a passenger vehicle. The algorithm is a combination of sliding mode control (SMC) and parameter adaptation. Initially, based on a 7-;degrees-;of-;freedom vehicle model, a sliding control law was designed to minimise the yaw rate error and to ensure that the side-;slip angle was within acceptable limits. To compensate for system parameter uncertainties, the control law was then updated using parameter adaptation factors that represented the unknown parameters. This integration allowed the derived controller to inherit the advantages of the sliding mode and adaptive control algorithms, including asymptotic stability from the adaptive system, and guaranteed transient performance from the SMC for both parametric and model uncertainties. The simulation results of the control system showed high performance even under critical operating conditions.