As the application of real time expert systems has been expanded, the real time expert systems have become an integral part of the information society. Real time expert systems are viewed as a new paradigm to integrate real time problem solving and expert system technology. However, a substantial amount of work is still required to effectively handle a new and challenging opportunity for successful implementation of real time expert systems. In this article, the basic concepts and characteristics of real time expert systems are discussed. The article also presents, through the literature survey, the summary of real time expert systems applications and a class of tools, providing an enabling real time based expert system technology. Finally, the article discusses a set of requirements which real time expert systems must satisfy.