This book constitutes the refereed proceedings of the Third International Conference on Artificial Immune Systems, ICARIS 2004, held in Catania, Sicily, Italy, in September 2004.The 34 revised full papers presented were carefully reviewed and selected from 58 submissions. The papers are organized in topical sections on applications of artificial immune systems; conceptual, formal, and theoretical frameworks; artificial immune systems for robotics; emerging metaphors; immunoinformatics; theoretical and experimental studies; future applications; networks; modeling; and distinguishing properties of artificial immune systems.