These proceedings contain the papers presented at the 5th Annual Genetic and Evolutionary Computation Conference (GECCO 2003). The conference was held in Chicago, USA, July 12–16, 2003.

A total of 417 papers were submitted to GECCO 2003. After a rigorous doubleblind reviewing process, 194 papers were accepted for full publication and oral presentation at the conference, resulting in an acceptance rate of 46.5%. An additional 92 submissions were accepted as posters with two-page extended abstracts included in these proceedings.

This edition of GECCO was the union of the 8th Annual Genetic Programming Conference (which has met annually since 1996) and the 12th International Conference on Genetic Algorithms (which, with its first meeting in 1985, is the longest running conference in the field). Since 1999, these conferences have merged to produce a single large meeting that welcomes an increasingly wide array of topics related to genetic and evolutionary computation.

Possibly the most visible innovation in GECCO 2003 was the publication of the proceedings with Springer-Verlag as part of their Lecture Notes in Computer Science series. This will make the proceedings available in many libraries as well as online, widening the dissemination of the research presented at the conference. Other innovations included a new track on Coevolution and Artificial Immune Systems and the expansion of the DNA and Molecular Computing track to include quantum computation.