This book constitutes the refereed proceedings of the 5th International Symposium on Mobile Human-Computer Interaction, Mobile HCI 2003, held in Udine, Italy in September 2003. The 21 revised full papers and 29 revised short papers presented together with a keynote paper and an abstract of a keynote speech were carefully reviewed and selected from 122 submissions. The papers are organized in topical sections on mobile users in natural context, input techniques for mobile devices, location-aware guides and planners, bringing mobile services to groups in workplaces, mobile gambling, tools and frameworks for mobile interface design and generation, and usability and HCI research methods