In this book, we have a clear, concise introduction, on the intermediate level, of all the tools necessary to handle the most important problems in electrodynamics, with emphasis on the experimental basis of significant phenomena. The book is divided into three parts: Phenomenological Elec­trodynamics, Electron Theory, and the Theory of Relativity. The first two parts present Maxwell’s Equations and their consequences, first intro­ducing phenomenological parameters to describe the behavior of material media and then deriving them from a more fundamental microscopic view. Einstein, through his Theory of Relativity, made possible a beautiful uni­fication of electric and magnetic phenomena. Therefore, a discussion of the historical background which led to Einstein’s theory, its fundamental concepts, and their far-reaching consequences may be found in the last part of this text. Principles of Electrodynamics, then, fills the need for a somewhat more advanced text on electricity and magnetism which does not assume great mathematical sophistication, but which does emphasize the basic physics.