Air-cooled condensers were first introduced into the U.S. power industry in the early 1970’s, but only began to increase in popularity during the last decade. The rising importance of this new and different technology for the condensing of steam has led to the need for a better understanding of the associated design, application, performance monitoring and cleaning requirements. This paper identifies the basic configuration of aircooled condensers in the power industry and some of the problems they encounter, especially fouling problems. Monitoring the performance of air-cooled condensers is an important task and the major criteria involved are identified. To rectify degradations in performance associated with external fouling, a number of cleaning procedures are described. Included among these are details of a new automated cleaning technology that has been successfully applied, and some of the performance improvements that have resulted from the use of this technique are presented.