Recent attention has been given to the energy and fuel economy benefits of replacing hydraulic power steering with electronically controlled electrohydraulic power steering (EHPS) systems for commercial vehicles. Given this emerging capability, investigation of the impact such systems would have on overall large truck stability is reported in this paper. In EHPS configurations, an electric motor is used to drive the hydraulic pump of the power steering system. This allows the assist torque gain to be modified by varying the speed and torque of the pump independently of engine speed. In the case of conventional hydraulic power steering, the pump is driven regardless of steering usage and presents a relatively constant load on the diesel engine. With EHPS, the electric motor drive allows for reduced draw of engine power by reducing or eliminating the torque assist when not needed. The development of small high-power motors has an area of ongoing research. Most EHPS drives are permanent magnet brushless motors with a three-phase MOSFET inverter to control pump speed and torque levels. This provides for improved fuel economy by reducing engine load such that the power steering pump is only active when needed for truck maneuvering. With use of handwheel torque sensors and additional hydraulic valves, on-demand' power steering systems have been developed and introduced into passenger vehicles. For the EHPS system considered in this research, a provision for measuring the articulation angle of the tractor-trailer is available through a multiplexed serial communication interface. It is found that varying the assist gain associated with the EHPS through the motor drive allows for improved stability of articulated vehicles. This paper first presents a method based on feedback of the rate of change in the articulation angle in conjunction with gain-scheduling to instantaneously vary the assist torque provided by the EHPS system. Experimental results of the design are evaluated through a hardwarein- the-loop (HIL) configuration that confirms the performance benefits of incorporating variable gain steering assist in large trucks.