This book constitutes the refereed proceedings of the 18th European Symposium on Programming, ESOP 2009, held in York, UK, in March 2009, as part of ETAPS 2009, the European Joint Conferences on Theory and Practice of Software. The 26 revised full papers presented together with two abstracts of invited talks were carefully reviewed and selected from 98 full paper submissions. The topics addressed are typed functional programming, computational effects, types for object-oriented languages, verification, security, concurrency, service-oriented computing, parallel and concurrent programming.