This book gives an introduction to H-infinity and H2 control for linear time-varying systems. Chapter 2 is concerned with continuous-time systems while Chapter 3 is devoted to discrete-time systems. The main aim of this book is to develop the H-infinity and H2 theory for jump systems and to apply it to sampled-data systems. The jump system gives a natural state space representation of sampled-data systems, and original signals and parameters are maintained in the new system. Two earlier chapters serve as preliminaries. Chapter 4 introduces jump systems and develops the H-infinity and H2 theory for them. It is then applied to sampled-data systems in Chapter 5. The new features of this book are as follows: The H-infinity control theory is developed for time-varying systems with initial uncertainty. Recent results on the relation of three Riccati equations are included. The H2 theory usually given for time-invariant systems is extended to time-varying systems. The H-infinity and H2 theory for sampled-data systems is established from the jump system point of view. Extension of the theory to infinite dimensional systems and nonlinear systems is discussed. This covers the sampled-data system with first-order hold. In this book 16 examples and 40 figures of computer simulations are included. The reader can find the H-infinity and H2 theory for linear time-varying systems and sampled-data systems developed in a unified manner. Some arguments inherent to time varying systems or the jump system point of view to sampled-data systems may give new insights into the system theory of time-invariant systems and sampled-data systems.