Networks of computers are making it possible to achieve computer-to-computer and terminal-to-computer communications that only a few years ago would have been impossible. Many of these networks are operational already, with more powerful ones seemingly in store for the future. This remarkable growth has opened new opportunities for designers, users, and managers?but it has posed some difficult problems for them as well. Knowledge of such network issues as topological design alternatives, common carrier communications services, value-added networks, hardware and software networking technology, cost factors, regulatory issues, measurement techniques, and network administration are of paramount importance. Hence this special issue.