Abstract: A steering booster system for a motor vehicle has an electronic control unit which senses by way of force or torque sensors the amount and direction of forces and torques applied to a manual steering wheel and correspondingly controls, via a transmission arrangement, the steering-force-assisting connection of an electric motor into a steering gear line coupling the manual steering wheel and the steered vehicle wheels. The manufacture of the system is simplified and the controllability of the force transmission between the electric motor and the steering gear line is improved by providing that the transmission arrangement has an electrically switchable clutch for each steering direction, i.e., left or right. The two clutches are arranged such that, when the rotating direction is the same at the input of the transmission arrangement assigned to the electric motor, they in each case cause another rotating direction at the output of the transmission arrangement assigned to the steering gear line.