This book constitutes the refereed proceedings of the 6th International Conference on Evolvable Systems, ICES 2005, held in Sitges, Spain in September 2005.

The 21 revised full papers presented were carefully reviewed and selected. The papers are organized in topical sections on fault tolerance and recovery, platforms for evolving digital systems, evolution of analog circuits, evolutionary robotics, evolutionary hardware design methodologies, bio-inspired architectures, and applications.