This paper is aimed to present the development of an automatic guidance system dedicated to a four-wheel steering vehicle. The attractive feature is that, despite of sliding phenomena, both lateral and angular deviations can be explicitly controlled with respect to the path to be followed. This is particularly useful to compensate the crabway motion on sloping terrain and maintain the direction of the vehicle parallel to the slope. On the contrary, in order to reduce soil compaction generally caused by the load of several wheels in the same track, the path following can be carried out with a chosen crab angle. Relying on a kinematic model extended with sliding parameters, a backstepping control approach is considered. Actual experiments carried out with a four-wheel-steering vehicle on a low adherent sloping terrain demonstrate the capabilities of the proposed control law.