As a discipline concerned with the design, evaluation and implementation of interactive computing systems for human use, and with the study of major phenomena surrounding them, human computer interaction (HCI) is involved in the phenomenon of disability. For an interaction between humans and computers to take place, there should be an interface mediating between both parties. The design of such an interface may inadvertently impose access barriers to some people. HCI literature addresses the relationship between the theory and practice of HCI and disability from different angles, some of which are diametrically opposed. This thesis explores three modern conceptions, or models, of disability — the individualistic medical, the biopsychosocial and the social models —, investigates which model predominates in the HCI literature, and analyzes why choosing a particular model may determine and constrain the classes of problems that can be identified during a solution discovery process. Departing from HCI’s traditional discourse, which interprets the phenomenon of disability as a problem in the human body, the author, leading a team of engineers and psychologists, carried out a project in a school for children with cerebral palsy. The project was aimed to improve different areas of child development, using non conventional user interfaces — i.e. user interfaces that use other input/output devices than the keyboard, mouse or screen. After two years working directly within the field of operations”, the author had the opportunity to contrast the theory underpinning HCI’s methods with real practice and to expand his understandings about the relationships between HCI and disability. The research process involved an action research approach, which allowed the author and the team of experimenters to formulate new hypotheses as they learned more about the context, to review the process and, ultimately and most importantly,to readapt their actions to better serve the end beneficiaries. The experiences and learnings gathered throughout the process have been included in this thesis as a case study, for the purpose of helping HCI researchers embarking on projects relatable to the one described. Finally, the author urges the HCI community to update its discourse and to connect it with the vast literature related to modern conceptions of the phenomenon of disability.