Abstract: An apparatus for measuring the lateral inclination of a supporting surface comprises a lateral inclination indicator (5) arranged on a vehicle (1). A second indicator (6) delivers information corresponding to the velocity of the vehicle. There are means (6, 7, 8) for delivering information corresponding to the velocity difference between the two laterally displaced wheels. A device (9) is adapted to, on basis of information from the second indicator (6) and said means (6, 7, 8) and information concerning the lateral displacement between the wheels, cause a correction, which corresponds to faults of information from the inclination indicator (5) resulting in consequence of laterally directed forces in curves, and by means of this correction and the information from the inclination indicator deliver an output signal corresponding to the real lateral inclination. (FIG. 1).