This volume contains the proceedings of the 20th Conference on Concurrency Theory (CONCUR 2009)
held in Bologna September 1-4 2009. The purpose of the CONCUR conference is to bring together
researchers developers and s-
dentsinordertoadvancethetheoryofconcurrencyandpromoteitsapplications. This year the CONCUR
conference was in its 20th edition and to celebrate 20 years of CONCUR the conference program
included a special session organized by the IFIP Working Groups 1.8 Concurrency Theory and 2.2
Formal - scriptionofProgrammingConceptsaswellas aninvitedlecturegivenby Robin Milner one of
the fathers of the concurrency theory research area. This edition of the conference attracted
129 submissions. We wish to thank all their authors for their interest in CONCUR 2009. After
careful discussions the Program Committee selected 37 papers for presentation at the
conference. Each of them was accurately refereed by at least three reviewers (four reviewers
for papers co-authored by members of the Program Committee) who delivered
detailedandinsightfulcommentsandsuggestions.TheconferenceChairswarmly thank all the members of
the Program Committee and all their sub-referees for the excellent support they gave as well
as for the friendly and constructive discussions. We would also like to thank the authors for
having revised their papers to address the comments and suggestions by the referees. The
conference program was enriched by the outstanding invited talks by Martin Abadi Christel
Baier Corrado Priami and as mentioned above Robin Milner.
