This volume contains the proceedings of the 14th International Conference on ConcurrencyTheory(CONCUR2003)heldinMarseille, France, September3 5, 2003. The conference was hosted by the UniversitedeProvenceandtheLa- ratoire d Informatique Fondamentale de Marseille (LIF). The purpose of the CONCUR conferences is to bring together researchers, developers, and students in order to advance the theory of concurrency, and promote its applications. Interest in this topic is continuously growing, as a consequence of the importance and ubiquity of concurrent systems and their applications, and of the...