The one-sideness observed in several extragalactic jets is usually explained by the Doppler boosting effect in a pair of relativistic beams, moving almost parallel to the line of sight. However jets could be intrinsically asymmetric if magnetically driven from the accretion disk surrounding the central black hole. Wang et al. (1992) have shown that a combination of odd and even magnetic structures could lead to different Poynting fluxes in the two hemispheres of the inner nucleus. However, without any peculiar assumption, it can be shown that intrinsic one-sideness can be simply related to the symmetry properties of the MHD equations.