This volume is a compendium of papers presented during the NATO Advanced Research Workshop which took place in Capri, Italy, October 12-18, 1986 on the general subject of "Flow Control and Congested Networks: The Case of Data Processing and Transportation". The focus of the workshop was on flow control methodologies, as applied to preventing or reducing congestion on data communication networks, on urban transportation networks and on air traffic control systems. The goals of the workshop included: - review of the state-of-the-art of flow control methodologies, in general, and in each of these three application areas; - identification of similarities and differences in the objective functions, modeling approaches and mathematics used in the three areas; - examination of opportunities for "technology transfers" and for future interactions among researchers in the three areas. Paralleling the structure of the workshop, the papers are organized into three groups: flow control of urban transportation networks (papers 1-9); flow control of data communication networks and some related or emerging methodological issues (papers 10-16); and, finally, flow control of air traffic (papers 17-21).