This paper provides a summary of the basic concepts of retrodirective antenna arrays. Originally this class of antenna was developed in the 1960s for direct satellite-to- ground transmission of high-power microwave energy. The recent explosive growth of mobile communications has, in the author’s opinion, reopened the debate for alternative applications of retrodirective array techniques. Advances in microstrip antenna design coupled with the availability of integrated circuit amplifier and mixer components permit minimum-complexity retrodirective antenna arrays to be constructed. Several different planar retrodirective antenna arrchitectures are presented and their basic operational characteristics given. A novel application for co-operatiing retrodirective antennas in a duplex communication page link with inherent space dividion multiple access capability is also described. Fibally some of the operational parameters which could ultimately limit the performanceof this class of antenna are discussed.