In this tutorial paper, we introduce a number of issues that arise in the design of distributed real-time systems in general, and hard real-time systems in particular. These issues include time management, process scheduling, and interprocess communications within both local and wide area networks. In addition, we discuss an evaluation, based on a simulation model, of a variety of scheduling policies used in real-time systems. Finally, we examine some relevant examples of existing distributed real-time systems, describe their structuring and implementation, and compare their principal features.