The study investigated the relationship between design and flexibility. Proposals by designers on how to incorporate the ability of buildings to accommodate changes in the requirements of the activities to be housed in buildings over time has led to a diversity of ideas regarding the relationship between suggested design variables and the achieved flexibility. Though a number of studies have been made on specific organisations and buildings, there has been no overall investigation of the general relationship between design and flexibility. To investigate this relationship it was necessary to: 1. Propose a system of measurement by which the extent of incorporation of the design variables in design proposals could be assessed (Chapters II and III). 2. Propose a system of measurement by which the extent of flexibility of buildings in use could be assessed (Chapter IV). 3. Assess the extent of flexibility achieved by the incorporation of design variables in design proposals by a study of actual buildings in use (Chapters V, VI, VII, and VIII). The study has largely achieved these objectives. It provided methods to enable objective comparison to be made between alternative design proposals in terms of the incorporation of design variables. It provided methods to enable objective comparison to be made between buildings in terms of their flexibility in use. It became apparent that the flexibility of buildings in use was related to only certain aspects of design variables or even to only certain parts of buildings. The study demonstrated that the flexibility of buildings in use is largely predictable from knowledge about their design. It showed that current ideas on flexible designs contain many factors that are redundant to flexibility. It recommends that future proposals of designing for flexibility need to be more refined than those at the present and that will enhance the effectiveness of manipulating the potential flexibility of buildings at the design stage. The main area of further research to emerge was concerned with the operationalisation of other design variables and their testing in various building types utilising the methods defined in this study.