The Editor of Artificial Life would like to express his gratitude to the people listed below, who anonymously refereed papers for the journal during the preparation of this volume (vol. 19). Their generosity, judicious judgment, and prompt response substantially helped us to publish a journal that both is timely and has exacting scientific standards. The responsibility for sustaining the quality and relevance of the journal largely rests in the hands of our reviewers. We at the journal, and all of our readers, are deeply indebted to them. It is a genuine pleasure to thank them collectively for their dedicated service. (Ifanyone has been inadvertently omitted from this list, we sincerely apologize and ask them to let us know so that we can include their name in a future list of referees.)

Shinya Aoi

Takaya Arita

Rachel Armstrong

Thomas J. Armstrong

Hugues Bersini

Joschka Boedecker

Michael Bowler

Ken Caluwaerts

Tomás Czárán

Ralf Der

Peter Dittrich

Marco Dorigo

Rene Doursat

Keith Downing

Harold Fellermann

Carlos Gershenson

Shogo Hamada

Helmut Hauser

Koh Hosoda

Shuhei Ikemoto

Akio Ishiguro

Jarko Kari

Hugo Gravato Marques

John McCaskill

Barry McMullin

Shuhei Miyashita

Ikuo Mizuuchi

Hiroyuki Mori

Norman Packard

Domenico Parisi

Jean-Paul Peronard

Rolf Pfeifer

Daniel Polani

Steen Rasmussen

James Reggia

Søren Riis

Hiroki Sayama

David Soloveichik

Hidenobu Sumioka

Takashi Takuma

Jun Tani

Kohji Tomita

Barry A. Trimmer

Rinie van Est

Peter Wills

Andy Wuensche