Most gases in nature are polyatomic, yet they are not considered in many textbooks of kinetic theory. In recent years they have been the subject of intensive research, and interesting results have been obtained which remain largely unknown. This book reviews the present state of knowledge of the kinetic theory of polyatomic gases, and is the first to provide a comprehensive account of both theoretical and experimental aspects of their behaviour.The first volume deals with dilute gases, in which boundary-layer effects can be neglected. Transport and relaxation phenomena such as heat conduction, diffusion, thermal diffusion, and viscous flow are considered from the point of view of kinetic theory. Special attention is paid to phenomena which do not occur in monatomic gases, including light scattering, nuclear spin relaxation, microwave absorption, and the effects of magnetic and electric fields on transport properties. Volume II begins by establishing the connections between molecular scattering theory and effective cross-sections in dilute gases,and then considers rarefied gases in detail.Detailed theoretical derivations are presented throughout the book, and experimental results and methods are documented in tables and figures. Introductory sections will be of use to graduates with a knowledge of elementary classical and quantum mechanics. The more specialized chapters are aimed at professionals who want information regarding the present state of the art in a particular field or who require data for various phenomena.