The use of compressed air techniques for the storage of energy is discussed in this chapter. This discussion begins with an overview of the basic physics of compressed air energy storage. The choice of location for compressed air energy storage for grid applications is then considered. The past use of compressed air energy storage is discussed and the current applications of advanced methods that improve efficiency and reduce environmental impact are presented. Non-grid applications of compressed air energy storage, such as transportation uses, are discussed. Finally, a method utilizing combined pumped hydroelectric and compressed air for energy storage is presented.