Quasielastic neutron scattering has made many important contributions to the atomistic elucidation of diffusion processes in solids. The aim of this book is to inform researchers in solid state physics, solid state chemistry, and inorganic materials science of the potential of quasielastic neutron scattering. It has been written in two sections for experimentalists. The first part contains theoretical background on neutrons, neutron scattering, and solid state diffusion, which is essential for the proper use of quasielastic neutron scattering; the second part of the book summarizes the scientific applications of quasielastic neutron scattering to special solid state materials systems, for example, to hydrogen in metals or to diffusion in solid state ionic conductors. The book is useful for both novices and current workers in this field.