Abstract: This paper describes an approach to three dimensional slope stability analysis.It is an extension of the 2 D Spencer’s.The new method allows the static equilibrium in all the three directions of the failure mass,with an additional condition satisfying the requirement for moment equilibrium.The number of assumptions made for the inter column forces has been reduced,compared to the other 3 D methods commonly used.This paper describes the results of some illustrative examples and applications in a number of engineering projects.