At present, the Amplitude-Magnitude (AM) method is largely applied for determining the spin axis direction of asteroids; such a method gives results which are in general in a good agreement with those
obtained by means of essentially different methods. However, one of the crltical assumptions of the AM method is that asteroids are modelled as triaxial ellipsoids with semiaxes a>b>c. Although
such an hypothesis appears reasonable for large objects on the basis of physical considerations about their expected equilibrium shapes, very irregular figures are more plausible for smaller objects, probably dominated by solid-state forces. Therefore, it is worth-while to study the influence that deviations from a purely triaxial ellipsoid shape can háve on the derived spin axis direction. For this purpose, a numerlcal program has been developed in order to compute the lightcurves of irregularly shaped objects at given aspect angles. The present paper reports some preliminary results concerning the uncertainty of the rotation axis direction of asteroids when non-triaxial shapes are considered.