Abstract: This invention relates to a rotary slide valve (5, 6) with a centering device (25) that is loaded by the force of a spring (31). The centering device is placed inside the valve housing (1) without any need for additional space in radial direction. In addition, the reaction pressure required by the steering system is reduced. According to the invention, spring (31) presses upon a reaction piston (32) that acts with a centering piece (24) upon the roller body (30) of the centering device (25). Between a lid (35) and the reaction piston (32), there is a reaction chamber (37) that can be provided with a variable pressure. At faster driving speeds, a pressure supporting spring (31) in the reaction chamber (37) acts upon the face (41) of the reaction piston (32). In this way, a smaller spring can be used and construction space can be saved because the force of the reaction pressure is additive with the force of the spring (31).