UbiComp 2003, the 5th Annual Conference on Ubiquitous Computing, is the premier forum for presentation of research results in all areas relating to the - sign, implementation, deployment and evaluation of ubiquitous computing te- nologies. The conference brings together leading researchers, from a variety of disciplines, perspectives and geographical areas, who are exploring the impli- tions of computing as it moves beyond the desktop and becomes increasingly interwoven into the fabrics of our lives. This volume, the conference proceedings, contains the entire collection of high-quality full papers and technical notes from UbiComp 2003. There were 16 full papers in this year’s conference, selected by our international program committee from among 117 submissions. There were also 11 technical notes in the program: 8 taken from the 36 technical note submissions, and 3 that were adapted from full paper submissions. We are very grateful to Tim Kindberg and Bernt Schiele, our Technical Notes Co-chairs, and to all the authors and reviewers of both papers and technical notes who contributed to maintaining the high standards of quality for the conference. In addition to the full papers and technical notes, UbiComp 2003 also p- vided a number of other participation categories, including workshops, dem- strations, interactive posters, a panel, a doctoral colloquium and a video p- gram. While accepted submissions in these categories were also of high quality, timing and size constraints prevented us from including them in this volume.