This book constitutes the refereed proceedings of the International Symposium of Formal Methods Europe, FME 2003, held in Pisa, Italy in September 2003. The 44 revised full papers presented together with 5 invited papers were carefully reviewed and selected from 144 submissions. The papers are organized in topical sections on industrial issues, control systems and applications, communication system verfication, co-specification and compilers, composition, Java, object-orientation and modularity, model checking, parallel processes, program checking and testing, B method, and security.