The submission is concerned with, and addresses, problems of designing for people with disabilities, with specific reference to people who are illiterate and cannot speak. People with such disabilities often depend on electronic AAC (Augmentative and Alternative Communication) devices for interpersonal communication. A central theme of the thesis, however, is that such products, and products intended for people with disabilities more generally, have characteristics that inadequately attend to users' needs. Through a combination of practical product development and literature reviews, the thesis demonstrates how improvements to AAC devices 'can be made through user-participatory, usercentred and more sensitive and perceptive design. Literature reviews in the following subjects are reported: AAC; the operational knowledge base for design and disability; user participatory design; and wearable computing. At the core of the thesis is the presentation and discussion of an empirical case study, carried out by the researcher, to design and develop the Portland Communication Aid (PCA). The PCA was conceived as an AAC product that would attempt to redress the inadequacies of predecessor devices. The design activity for the PCA is traced in the thesis, from initial concepts and development models through to a working prototype. Key ideas and essential principles of the design are illustrated. Throughout the work on the PCA, many problems associated with designing for people with severe communication disabilities were encountered. These problems, as with their resolutions, comprised matters of both designing (as an activity) and design (as product specification). The thesis contains comprehensive exposure and analysis of these problems and resolutions. In particular, the value of shaping meaning, metaphor, and other product semantics into devices intended for use by people with disabilities is explored. The study provides two substantive conclusions. First, that both the activity and the outcomes of Industrial Design have a valuable role in the empowerment and rehabilitation of AAC users. And second, that key principles have been identified that will enable designers to better identify, articulate and respond to the needs of people with communication disabilities (and the needs of people with disabilities more generally)