An expert system approach to solve the problem of generation expansion planning is presented. The approach is based on the decision tree technique which is used instead of the currently used techniques of mathematical programming. The expert system approach is capable of emulating human expertise in the field of generation planning. New concepts based on the natural properties of the problem are developed to minimise the computation burden by making in the minimum size. The solution technique satisfies the current objectives of strategic planning and is capable of modelling the various uncertainties inherent in the problem of generation expansion planning.