This book constitutes the refereed proceedings of the 20th International Conference on Concurrency Theory, CONCUR 2010, held in Paris, France, August 31 - September 3, 2010. The 35 revised full papers were carefully reviewed and selected from 107 submissions. The topics include: - Basic models of concurrency such as abstract machines, domain theoretic models, game theoretic models, process algebras, and Petri nets. - Logics for concurrency such as modal logics, probabilistic and stochastic logics, temporal logics, and resource logics. - Models of specialized systems such as biology-inspired systems, circuits, hybrid systems, mobile and collaborative systems, multi-core processors, probabilistic systems, real-time systems, service-oriented computing, and synchronous systems. - Verification and analysis techniques for concurrent systems such as abstract interpretation, atomicity checking, model checking, race detection, pre-order and equivalence checking and run-time verification.