The purpose of the present book is to acquaint the reader with some applications of interval analysis in electric circuit theory. More specifically, interval models and ensuing interval methods for circuit analysis are presented in detail for the following topics: linear electric circuit tolerance analysis (steady-state as well as transient analysis); linear circuit stability and nonlinear circuit analysis (including both resistive and dynamic circuits). In order to make the book self-contained a comprehensive survey of all the necessary interval analysis notions and techniques is provided in the introductory text. Most of the theoretical developments considered in the book are illustrated through numerical examples.