Properties of the effective cross sections which have been utilized in the expressions for nonequilibrium phenomena in dilute polyatomic gases are discussed, and interrelationships amongst them elucidated. Then, the evaluation of such effective cross sections from molecular scattering theory is outlined. The temperature dependence of the effective cross sections as determined experimentally is discussed, and for molecular hydrogen, compared with the results of full quantum scattering calculations. Transport phenomena in rarefied gases, the modelling of the surface scattering operator and the derivation of boundary-layer effects (with and without magnetic fields present) are covered in four chapters. Aspects of the collisionless gas regime are then dealt with in a separate chapter. The penultimate chapter covers relevant mathematical material, and the final chapter provides tables of experimental data and effective cross sections deducted from these data wherever possible. This book completes this major two-volume work on Non-equilibrium phenomena in polyatomic gases, and stands as a definitive treatise in this area of chemical physics. Volume 1, on dilute gases, was published in August 1990.