One of the main fields of study in the control of dynamical systems has been the effective control of time-varying systems with uncertain parameters and external disturbances. In contrast to stochastic adaptive controllers with identification algorithms, the deterministic control of uncertain time-varying systems has a fixed nonlinear feedback controller, which operates effectively over a specified magnitude range of a class of system variations. If the variations satisfy certain matching conditions, complete insensitivity to system uncertainties can be achieved. The two main approaches are Variables Structure and Lyapunov control. The contents of this book reflect the research output of many authors. The chapters include material of an introductory nature as well as some of the latest research results. Attention has also been focussed upon some of the main areas of application, which include electric motor drives, robotics and flight control systems. The book should prove useful to control designers, theoreticians and graduate students.