The bibliography on electromagnetism is very rich and it may be necessary to justify our effort in writing a new text. The present text arose as a need when lecturing about the subject at Instituto Balseiro, in Bariloche, Argentina. We wanted to have a reference text for the most important topics covered in the course, which would also cover some aspects of interest for the applications of the concepts that the students have learned. follows one in classical mechan­ A course on electromagnetism usually ics. In the latter a brief introduction to the theory of relativity is normally included. During courses on electromagnetism this theory is traditionally presented again in brief form. This approach has the effect that, unless students later work on related topics, they do not acquire an appropriate knowledge of relativity. In this way, they lose perspective of the importance of one of the most beautiful and fascinating creations of physics in the twentieth cen­ tury. For this reason,we consider the properties of charges, currents and electromagnetic fields in vacuum, highlighting the relativistic transformation properties of each quantity. In spite of the advantages and elegance of the co­ variant formulation of electromagnetism, however, we avoid overemphasizing it. It is left for Chap. 9, where we present it after having developed vacuum electrodynamics. In this way, we minimize the risk of negatively impressing those students who are attracted to more concrete problems.