Molecular Collisions and Gaseous Kinetics covers elastic collisions, inelastic collisions leading to energy transfer and electronic transitions, reactive collisions, and photoinduced dynamics. It also covers collisions with surfaces, thermal rates of those phenomena, as well as transport and relaxation phenomena mediated by molecular collisions. The book ends with a chapter on many-atom scattering theory as an introduction to more advanced descriptions. The treatment is based on the quantal theory of scattering and its semiclassical limits, introduces realistic intermolecular forces, and includes computational aspects needed to calculate cross-sections and compare them with experimental data. It is motivated by a need to cover these subjects starting from the electronic structure and atomic conformation of molecules. The chapters provide an introduction to experimental methods where appropriate, and connect theory to applications for specific physical systems to obtain results that can be compared to experimental data.