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. Building on the success of the previous WCW meetings, WCW 2004 extended its scope and covered interesting research and deployment areas relating to content services as they move through the Internet. This year, WCW was held in Beijing, China. Although it was the first time that WCW was held in Asia, we received more than 50 high quality papers from five continents. Fifteen papers were accepted as regular papers and 6 papers as synopses to appear in the proceedings. 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. We would like to take this opportunity to thank all those who submitted papers to WCW 2004 for their valued contribution to the workshop. 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.