This book constitutes the refereed proceedings of the 5th International Conference on Formal Engineering Methods, ICFEM 2003, held in Singapore in November 2003.The 34 revised full papers presented together with 3 invited contributions were carefully reviewed and selected from 91 submissions. The papers are organized in topical sections on testing and validation, state diagrams, PVS/HOL, refinement, hybrid systems, Z/Object-Z, Petri nets, timed automata, system modelling and checking, and semantics and synthesis.