This book contains a collection of the best papers presented at the 5th International Conference on Interacción Persona Ordenador (IPO), Human Computer Interaction in Spanish, which took place in Lleida on May 5th-7th, 2004. In its fifth edition this conference has become a multidisciplinary forum for the discussion and dissemination of novelty research in Human Computer Interaction. The main goal of Interacción 2004 was to expand the conference scope with internationally recognised invited speakers. Other goals such as enriching the relationship between industry and academia through the organisation and assisting the development of doctoral dissertations of high quality were also achieved. This book is organised according to the main areas of both basic and applied research that were presented at the conference. These areas were: Usability and Accessibility, Ubiquitous computing and context aware systems, Interaction with learning recourses, User Centred design methodologies, Cooperative systems, Models of interactive systems, Applications of User Centred design, Information of Visualization, HCI methodologies, Semantic web Group learning and work. This work is suitable for all scientists interested in HCI research.