Study of several field case histories has shown that the difference between two - and three - dimensional factors of safety is most pronounced in cases that involve a translational failure. Two and three dimensional slope stability analysis of field case histories and a parametric study of a typical slope geometry revealed that commercially available three dimensional slope stability programms have a number of limitations with respect to (1) accounting for the shear resistance along the sides of the sliding mass; (2) modeling the stress dependent nature of failure envelopes of the materials involved and (3) considering the internal forces in the slide mass. These limitations can significantly affect the calculated factor of safety for a translational failure mode. A technique is presented to overcome some of these limitations and provide a better estimation of the three dimensional factor of safety.