The conventional method to evaluate earthquake induced PERMANENT deformations of slopes is the one proposed by Newmark. In this paper, PERMANENT DISPLACEMENT of slopes is studied using a combination of distinct element ancl finite difference methods and the results of these numerical evaluations are compared with those of the Newmark's approach. Several parameters involved, including peak ground acceleration, period of excitation, friction and cohesion of the sliding surface, are considered in this study. The results show that the period of excitation is an important parameter in finding the DISPLACEMENTs of slopes. In addition, it is shown that in resonance condition, the PERMANENT DISPLACEMENT of a slope, derived by Newmark's method, can be twice the one predicted by the distinct element method. Finally, It is realized that, in frictional materials, PERMANENT DISPLACEMENTs of slopes obtained by the distinct element and Newmark's methods are in better agreement compared with the corresponding results in cohesive materials.