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.