This book constitutes the thoroughly refereed post-proceedings of the 6th International Conference on Artificial Evolution, EA 2003, held in Marseilles, France in October 2003.The 32 revised full papers presented were carefully selected and improved during two rounds of reviewing and revision. The papers are organized in topical sections on theoretical issues, algorithmic issues, applications, implementation issues, genetic programming, coevolution and agent systems, artificial life, and cellular automata.