This monograph aims at giving an extensive treatment of modeling issues, design methodologies and implementation aspects, arising when the adaptive control theory is applied to nodal voltage control in power systems. The monograph is structured into six chapters and an appendix. The first three chapters introduce the reader to the voltage control problem and the subsequent three chapters illustrate different design methodologies. In particular the first chapter describes the power system control problem and the voltage control structures adopted in transmission, distribution and industrial electrical systems. The second chapter presents power system models that can be usefully employed in voltage control design. The third chapter studies the properties of the Kalman filter used in the estimation of voltage and current phasors. The subsequent two chapters deal with the discrete-time design of, respectively, self-tuning and model-reference adaptive voltage controllers. The sixth chapter illustrates an adaptive design that is quite different from those presented in the two previous chapters, being based on an adaptive mechanism compensating the power system model nonlinearities. Finally, the appendix describes the high-voltage transmission system and industrial network used in the simulations reported in the monograph.