This overview provides a general description of the International Energy Evaluation System (IEES). The discussion emphasizes methodology, capabilities, and uses of IEES rather than implementation details. Discussed are the history and evolution of the current IEES model, and the model's purposes and capabilities. A review of the model's structure is presented, followed by a discussion of major modeling assumptions intrinsic to the system. Applications of IEES and the approach to developing IEES analysis scenarios, limitations of IEES and alternative modeling approaches, and the IEES output reports are described.