This book presents surveys on the theory and practice of modelling, specifying, and validating concurrent systems. It contains surveys of techniques used in tools developed for automatic validation of systems. Other papers present recent developments in concurrency theory, logics of programmes, model-checking, automata, and formal languages theory. The volume contains the proceedings from the workshop, Partial Order Methods in Verification, which was held in Princeton, NJ, in July 1996. The workshop focused on both the practical and the theoretical aspects of using partial order models, including automata and formal languages, category theory, concurrency theory, logic, process algebra, programme semantics, specification and verification, topology, and trace theory. The book also includes a lively e-mail debate that took place about the importance of the partial order dichotomy in modelling concurrency.