This project concerns the development of new theory and techniques dealing with the analysis and synthesis of control systems in the presence of uncertainty. The main outcome of this project is a theory that provides a systematic means for designing controllers which lead to systems possessing optimal stability and performance properties despite the presence of plant and signal uncertainty. This theory is based on the structured uncertainty model which allows the inclusion of information about the sources of modelling uncertainty thus minimizing conservatism in the analysis and design procedures. In addition, by adopting the l-infinity signal norm, time domain objectives can be included in the design in a natural way. The use of this norm distinguishes this approach from other approaches and provides a novel way for addressing the issues involved in controlling uncertain systems. The methods employed in the project will take advantage of recently developed theory which makes possible the analysis of system stability and performance robustness. Numerical algorithms implementing the developed controller synthesis techniques will also be developed and applied to practical examples. In addition, the theory for robustness analysis will be extended to incorporate a larger class of systems and to allow a better representation of disturbances and uncertainty.