An electric power steering system for an automotive vehicle, including a steering torque detecting device which detects a steering torque of a steering shaft. An electric motor is provided to generate an assist torque for assisting a driver's steering effort required for steering the vehicle and a counter-assist torque for increasing the driver's steering effort. The assist torque and the counter-assist torque are applied to a steering mechanism. Additionally, a controller is provided to output a drive command to the electric motor in accordance with the detected steering torque. The drive command is for causing the electric motor to generate the counter-assist torque when the detected steering torque is a transitional torque.