Abstract: A hydraulic power steering system for non-tracked vehicles, particularly motor vehicles, has a steering adjustment of the steered vehicle wheels which takes place of a hydraulic actuating assembly which can be connected by a change-over valve with one respectively of two or several hydraulic circuits. In normal operation, the circuits operate in parallel and functionally in the same direction so that, in the event of a disturbance, a change-over can take place to another hydraulic circuit without any interruption. For controlling the actuating assembly, each hydraulic circuit comprises a servo valve which is operated as a function of a desired-actual value comparison of the steering angle by a control and automatic control device, which is connected with an actual steering angle value generator operated by the steered vehicle wheels and a desired steering angle value generator controlled by way of the steering handle operated on the driver side.