Book excerpt: This book constitutes the refereed proceedings of the 17th International Conference on Concurrency Theory, CONCUR 2006, held in Bonn, Germany in August 2006. The 29 revised full papers presented together with 5 invited papers were carefully reviewed and selected from 101 submissions. The papers are organized in topical sections on model checking, process calculi, minimization and equivalence checking, types, semantics, probability, bisimulation and simulation, real time, and formal languages.