This article deals with the influence of dislocations on the conductivity of two dimensional electron gas measured at helium temperature and at high magnetic field. Two kinds of dislocation substructures have been experimentally studied: they correspond either to a family of parallel dislocation segments introduced by plastic bending or to a family of parallel and long misfit dislocations created during the epitaxial growth by the control of the epilayer thickness. It is shown that both types of dislocation substructure lead to a strong anisotropic behavior of the longitudinal conductivity while the quantum Hall effect is not significantly affected by the presence of dislocations. A theoretical treatment of the case of anisotropic potentials is proposed as a generalization of the simpler case, addressed in the literature, of isotropic (short range) potentials. With the help of this analysis, we can explain, in the case of the dislocation segments, why although anisotropic, the normalized conductivity curves obtained in the principal axis are identical and we show that regular Dingle plots may be used to check the extra broadening of the Landau levels due to dislocations. The second kind of dislocation substructure is shown to be equivalent to quasi one dimensional systems issuing from a truncation of the two dimensional electron gas into quite parallel ribbons localized between the dislocation potential barriers, but no ballistic effects could be observed. ©1996 American Institute of Physics.