Geotechnical engineering design includes a great deal of uncertainty because of the natural heterogeneity of soils and the limited extend of in-situ geotechnical investigation. The assumption that soil consists of layers with some average values for soil parameters of each layer does not offer a realistic representation of the actual conditions. Therefore, there is a need to use stochastic methods for the analysis of the stability of slopes in order to incorporate as many as possible types of uncertainty, including the spatial variability of soil properties. The uncertainties associated with the determination of the mechanical properties of the slopes and the intensity of the seismic excitation, make such probabilistic calculation methods very attractive. As opposed to deterministic methods, probabilistic methods allow the selection of an acceptable risk level based on the specifications of each project.The parameters of shear strength may vary from point to point even in the same soil layer as a result of the natural heterogeneity. Stochastic methods have been introduced to take into account the uncertainty and spatial variability of soil parameters using the Random Field Theory. The adopted methodology takes into account the cross-correlation between various properties and the autocorrelation of each property in the horizontal and vertical directions. Among the various available random field generating algorithms, the very effective methodology of Local Average Subdivision method (LAS) proposed by Fenton and Vanmarcke (1990) is utilized in the present study.The main objective of this study is to investigate the above problem using probabilistic and stochastic methods in order to attain the most realistic description of the variation of the slope static safety factor and the permanent displacements resulting from seismic excitations. This is achieved by combining the algorithm for generating random fields with the finite difference program FLAC (Fast Lagrangian Analysis of Continua) for the static analysis, ...