The approach to physical kinetics is closely integrated with that of other branches of physics as presented in the companion volumes of this series. The major part of the contents is concerned with a systematic development of the theory of plasmas, the authority being firmly rooted in the pioneer work of Landau. Although the main scope concerns fully ionized gaseous plasmas, corresponding results are also given for partially ionized plasmas, relativistic plasmas, degenerate or non-ideal plasmas and solid state plasmas. Problems (with answers) are to be found in the text. This work completes the Course of Theoretical Physics begun over 20 years ago