Book excerpt: This book constitutes the thoroughly refereed post-proceedings of the 5th International Workshop on Engineering Societies in the Agents World, ESAW 2004, held in Toulouse, France, in October 2004. The 23 revised full papers presented together with an invited paper went through two rounds of reviewing and improvement and were carefully selected from 48 initial submissions. The papers are organized in topical sections on roles, organizations, and institutions for agents; social issues in multi-agent systems; cooperation and collective behavior in agent societies; methodologies and platforms for agent-oriented engineering; agent-oriented simulation; and models for multi-agent systems.