This year, WCW was held in Beijing, China.
The topics covered included architectural issues, routing and placement, caching in both traditional content delivery networks as well as in peer-- peer systems, systems management and deployment, and performance evaluation. This event would not have been possible without the broad and personal support and the invaluable suggestions and contributions of the members of the program committee and the steering committee. We would like to take this opportunity to thank all those who submitted papers to WCW 2004 for their valued contribution to the workshop. Since the start of the International Workshop on Web Caching and Content Distribution (WCW) in 1996, it has served as the premiere meeting for researchers and practitioners to exchange results and visions on all aspects of content caching, distribution, and delivery.