Arti?cial Immune Systems have come of age. They are no longer an obscure computersciencetechnique,workedonbyacoupleoffarsightedresearchgroups. Today, researchers across the globe are working on new computer algorithms inspired by the workings of the immune system. This vigorous ?eld of research investigates how immunobiology can assist our technology, and along the way is beginning to help biologists understand their unique problems. AIS is now old enough to understand its roots, its context in the research community, and its exciting future. It has grown too big to be con?ned to s- cial sessions in evolutionary computation conferences. AIS researchers are now forming their own community and identity. The International Conference on Arti?cial Immune Systems is proud to be the premiere conference in the area. As its organizers, we were honored to have such a variety of innovative and original scienti?c papers presented this year. ICARIS 2004 was the third international conference dedicated entirely to the ?eld of Arti?cial Immune Systems (AIS). It was held in Catania, on the beautiful island of Sicily, Italy, during September 13–16, 2004. While hosting the conference, the city of Catania gave the participants the opportunity to enjoy the richness of its historical and cultural atmosphere and the beauty of its natural resources, the sea, and the Etna volcano.