Applications of computers in the planning of power system generation, transmission, and distribution are surveyed. Following a brief description of significant developments in the growth of these applications over the 22 years since the first published paper, the stages in planning (policy, standardization, outline, and detail design) and the mathematical techniques which can be applied to the numerical solution of quantifiable problems arising in these stages are outlined. The greatest concern is with the technical and economic studies commonly used in the major areas of planning, i.e., load forecasting, assessment of generation capacity and mix, transmission and distribution network development. Approaches using simulation and optimization techniques are described. Reference is made to developments in corporate planning.