This book constitutes the refereed proceedings of the 9th European Conference on Artificial Life, ECAL 2007, held in Lisbon, Portugal, September 10-14, 2007.

The 125 revised full papers presented were carefully reviewed and selected. The papers are organized in topical sections on conceptual articles, morphogenesis and development, robotics and autonomous agents, evolutionary computation and theory, cellular automata, models of biological systems and their applications, ant colony and swarm systems, evolution of communication, simulation of social interactions, self-replication, artificial chemistry, and posters.