This book is a research monograph describing results obtained by the author and his co-workers of the last two years. It deals with the feedback stabilization of linear time invariant systems containing a real parameter vector subject to perturbation. The results described include methods for designing low order regulators for the nominal plant, the calculation of stability regions and stability margins in the parameter space, and procedures to design stabilizing controllers that tolerate prescribed ranges of parameter perturbations. Each of these problems is treated in the transfer function and state space domains. Results are presented at the theoretical level and at the algorithmic computational level. The purpose of this monograph is to present - at an elementary level - some promising preliminary results and to draw the attention of researchers to this class of problems. The book is intended for control theorists, applied mathematicians and engineers involved in control systems research and development.