We welcome you to the proceedings of the 5t International Conference on E- CommerceandWebTechnology(EC-Web2004)heldinconjunctionwithDEXA 2004 in Zaragoza, Spain. This conference, ?rst held in Greenwich, United Ki- dom in 2000, now is in its ?fth year and very well established. As in the four previous years, it served as a forum to bring together researchersfrom academia and commercial developers from industry to discuss the current state of the art in e-commerce and Web technology. Inspirations and new ideas emerged from intensive discussions during formal sessions and social events. Keynote addresses, research presentations and discussions during the c- ference helped to further develop the exchange of ideas among the researchers, developers and practitioners present. The conference attracted 103 paper submissions and almost every paper was reviewed by three program committee members. The program committee - lected 37 papers for presentationand publication, a task which was not easy due to the high quality of the submitted papers. We would like to express our thanks to our colleagues who helped with putting together the technical program: the program committee members and external reviewers for their timely and rigorous reviews of the papers, and the organizing committee for their help in the administrative work and support. We owe special thanks to Gabriela Wagner, Mirella Köster, and Birgit Hauer for their helping hands concerning the administrative and organizational tasks of this conference. Finally,wewouldliketothankalltheauthorswhosubmittedpapers,authors who presented papers, and the participants who together made this conference an intellectually stimulating event through their active contributions.