This book constitutes the thoroughly refereed post-proceedings of the 4th International Workshop on Engineering Self-Organising Applications, ESOA 2006, held in Hakodate, Japan in May 2006. This was an associated event of AAMAS 2006, the 5th International Joint Conference on Autonomous Agents and Multi-Agent Systems. The seven full papers presented together with six invited papers were carefully selected for inclusion in the book.
