  This volume contains the proceedings of the 18th International Workshop on
Expressiveness in Concurrency (EXPRESS 2011), which took place on 5th September
2011 in Aachen, as a satellite workshop of CONCUR 2011. The EXPRESS workshop
series aim at bringing together researchers who are interested in the
expressiveness and comparison of formal models that broadly relate to
concurrency. In particular, this also includes emergent fields such as logic
and interaction, game-theoretic models, and service-oriented computing.
