This advanced-level textbook is intended for use on courses in nonlinear systems/control, in departments of electrical engineering, control engineering and mathematics. This revised edition includes updated and new material on feedback linearization, I/O systems, adaptive control and discrete time systems. The text deals with all basic methods (phase plane, describing function, point transformation, Tsypkin, Lyapunov) used in the analysis and design of nonlinear control systems. Modern developments (chaotic motion, variable-structure systems, absolute stability, adaptive control) are introduced, and the text presents an analysis of how nonlinearities affect performance of control systems and methods of overcoming deleterious effects. Nonlinear effects in sample-data systems, essential in modern digital control, are examined. Numerous examples illustrate the application of analytical methods to cases taken from a variety of fields where nonlinear systems occur.