This book constitutes the refereed papers of the 11th International Conference on Concurrency Theory, CONCUR 2000, held in University Park, PA, USA in August 2000. The 34 revised full papes presented together with eight invited talks or tutorials were carefully reviewed and selected from 72 submissions. The papers address concurrency-related aspects of models of computation, semantic domains, process algebras, Petri nets, event structures, real-time systems, hybrid systems, decidability, model checking, verification techniques, refinement, term and graph rewriting, distributed programming, logic constraint programming, object-oriented programming, typing systems and algorithms, case studies, tools, and environments for programming and verification.