Book excerpt: This book constitutes the thoroughly refereed post-proceedings of the 4th International Workshop on Engineering Societies in the Agents World, ESAW 2004, held in London, UK in October 2004. The 23 revised full papers presented were carefully selected during two rounds of reviewing and improvement for inclusion in the book; also included are 2 invited papers by leading researchers in order to round of the coverage of the relevant topics. The papers are organized in the following topical sections: - multidisciplinary for agent societies - coordination, organization, and security of agent societies - abstractions, methodologies, and tools for engineering agent societies - applications of agent societies