This research was aimed at producing new control concepts to serve future generations of larger and more flexible spacecraft. The need to employ gas jet actuators, at least for some operational phases, promoted this research. The non-specialist is provided with an introduction to spacecraft attitude control. The mathematical models of flexible spacecraft used in later chapters are then derived. Existing attitude control techniques and the approaches of other authors are then discussed. This is accompanied by a brief account of the author’s past research in the field. Thus, a foundation is layed for the generation of the new control concepts. The use of finite order models, as required in a state space approach, is justified by means of a mode spillover study. Here, it is shown that gas jets may be used safely in the presence of unmodelled flexure modes. A new ’fine pointing’ gas-jet control law is then postulated and developed for single axis models. This is followed by an extension to cater for heavy cross-coupling between two control axes. The fine pointing control law is found to be stable only in a finite region enclosing the origin of the state space. A new ’large error’ control law is then derived to bring the state witnin the capture region of the ’fine pointing' control law. The use of state estimators is then considered. This facilitates a study of the control loop responses to transient disturbance torques, including dynamics parameter mismatches. The reported research has provided a feasible approach to the gas-jet control of flexible spacecraft. The algorithms derived are immediately applicable to certain types of spacecraft. Suggestions are given for further research aimed at extension to more general spacecraft configurations.