The present volume comprehensively summarizes the late Julian Schwinger’s work on the theory of electromagnetic radiation and its application to waveguides, transmission lines, accelerator physics and synchrotron radiation. The first part, written in textbook style, has grown out of lectures and manuscripts by Julian Schwinger prepared during the war at MIT’s Radiation Laboratory, updated with material developed by Schwinger at UCLA in the 1970s and 1980s, and by Milton at the University of Oklahoma since 1994. The second part consists of reprints of more than 15 papers (some of them never published or available with very limited circulation) by Schwinger on these topics. This volume will be of great interest to physicists, electrical engineers and applied mathematicians whether they be students or seasoned professionals. A paperback study edition of the first part is available separately.