Communicating Process Architectures 2008 contains the proceedings of the thirty-first Communicating Process Architectures Conference (CPA 2008) organized under the auspices of WoTUG and the Department of Computer Science of the University of York. The aim of this book is to cover both theoretical aspects and industrial applications of Communicating Processes. Two invited speakers have given excellent contributions to this topic. Professor Samson Abramsky has worked in the areas of semantics and logic of computation, and concurrency. His work on game semantics considers interaction and information flow between multiple agents and their environment. This has yielded new approaches to compositional model-checking and to analysis for programs with state, concurrency, probability and other features. Professor Colin O'Halloran has been instrumental in the uptake of formal methods in the development and verification of high assurance systems on an industrial scale. His research interests are in automating the use of formal methods, and using these techniques at reasonable cost and on an industrial scale.