Quality online health information/knowledge is globally in high demand. Achieving such quality necessitates a multi-disciplinary requirements engineering approach that enables elicitation, analysis and representation of the viewpoints from a broad variety of related sources. These sources include health and health education/promotion professionals, health informaticians and application design experts, and health consumers, the primary users of such knowledge. In addition, maintaining and improving quality over time requires such a large set of viewpoints to be updated regularly. This dissertation endeavors to provide an enabling methodology to address the above needs specifically in the field of eHealth. This research was conducted in two steps. In the first step, the existing methods of requirements engineering applicable into our particular scope of eHealth applications, aimed at health promotion/education, were reviewed to develop a framework for knowledge requirements engineering. In the second step, the usability and usefulness of the proposed framework were evaluated throughout a four-phase study (0-III). During this study, knowledge requirements engineering was used to specify the pieces of information that should be included in a quality health Web site targeting university students. Within the established framework, requirements data was gathered from various sources, including literature, existing Web sites, and interviews with local health professionals and university students. The evaluation results showed that the pieces of information and health topics specified using the framework consistently matched those the subjects preferred. In addition, the findings provided evidence that such information, when used by health search engines to index and retrieve online health resources, helped the subjects choose the resources that actually matched their interest. Finally, the data showed a higher satisfaction of the subjects with the health Web site that was built based on the knowledge requirements specified, as compared to the other selected health Web sites. This dissertation makes significant contributions to the fields of health informatics, health promotion, and requirements engineering. It contributes to the field of health informatics by expanding the scope of requirements engineering to include the field of eHealth and knowledge provision. The approach presented illustrates how various viewpoints related to requirements knowledge should be elicited, analyzed, and reasoned to build valid knowledge requirements specifications representing viewpoints of all sources consulted. It also illustrates how such specifications can be used as a basis to build quality eHealth applications. In the field of health promotion, this dissertation demonstrates a knowledge provision methodology that is grounded in the models of health behaviour change. This methodology allows health educators to rationally and accurately specify not only the health topics of high interests to health consumers, but also the type of knowledge they would prefer to be provided in the related knowledge artifacts. More particularly, this research has specified the health knowledge content of preference to adolescent consumers. These specifications highlight the particular knowledge needs of this age group, which can be used as a basis for local to national health promotion activities targeting these consumers. Finally, the research contributes to the field of requirements engineering by illustrating an integrated requirements engineering approach that accommodates multiple viewpoints and allows transparent reasoning and representation of requirements. It is anticipated that the concept of knowledge requirements engineering introduced and discussed in this dissertation will open a new area of research and practice for health informaticians. Subsequently, the methodology demonstrated can be improved and further advanced to address the needs of other domains of health and health-related knowledge.