Designers draw on a significant volume and range of information throughout the design process. This could include information on people, materials, markets, processes, etc. However, not all this information is effectively communicated to and used by designers. In order to provide designers with information that is useful, useable and engaging for them, it is important to understand why designers use information, what information they use and when and how they use it. This will be collectively referred to as ‘information behaviour’ in this thesis. There is currently a lack of a holistic understanding of designers’ information behaviour. Through developing a framework for investigation, analysis and reflection on designers’ use and requirements of information, this research aims to provide a better understanding of information behaviour in design, leading to a systematic way to address the key dimensions of information used in a design process. For this purpose, the research focuses on ‘practicing designers’ as key users of information in the real-world practice of design and ‘people information’ as a major type of information used during the design process. An initial framework for addressing key dimensions of information used in the design process is outlined through the analysis and synthesis of relevant literature. The framework is then evaluated and refined through four complementary studies: an interview and questionnaire administered to nine design companies; observation of a design team in a real-world design project; observation of three teams through a design competition; and a survey of designers and design researchers. The outcomes of the studies lead to a refined version of the information framework that includes seven key dimensions and details designers’ behaviour in regard to ‘purpose’, ‘source’, ‘format’, ‘type’, ‘at tributes’, ‘stage’ and ‘intensity’ of people information they use. The research conducted with designers leads to an enhanced understanding of their information behaviour with respect to the seven key dimensions. A new information framework has been created and evaluated; and it is argued that it can be used as a research and education tool to investigate and analyse information used during core stages of a design process. The framework can also assist developers of information tools to make informed decisions on what, how and when to communicate information to designers, ensuring that this information is delivered in a way which has maximum impact on the design process.