This book constitutes the refereed proceedings of the Third International Conference on Embedded Software, EMSOFT 2003, held in Philadelphia, PA, USA in October 2003. The 20 revised full papers presented together with three invited papers were carefully reviewed and selected from 60 submissions. All current topics in embedded software are addressed: formal methods and model-based development, middleware and fault tolerance, modeling and analysis, programming languages and compilers, real-time scheduling, resource-aware systems, and systems on a chip.