The book describes the application of piezoelectric materials, e.g. piezoceramics, in the wide field of actuators and sensors. It gives a step-by-step introduction into the structure and mechanics of piezoelectric beam bending actuators in multilayer technology, which are of increasing importance for industrial applications. The dynamic behaviour of piezoelectric multilayer beam benders is described on the basis of the powerful Lagrangian formalism and Hamiltons principle. Then follows a systematic development of the electromechanical circuit representation for any kind of piezoelectric beam bending actuators within the framework of the electrical network theory. Two different sensor-actuator systems based on a capacitive and an inductive sensor principle are presented and discussed in detail. Analytical simulations of the static and dynamic behaviour are compared to real measurement results of a specially developed piezoelectric multilayer beam bender. Here the suitability of the developed theoretical aspects is shown in an outstanding way.