The dynamics of atoms and molecules in solids and liquids can now be investigated in great detail using quasielastic neutron scattering. The suitability of slow neutrons for this purpose arises from their energies being comparable with the heights of the barriers which prohibit molecular reorientations, and their wavelengths being similar to interatomic distances. These features allow both temporal and geometrical information to be obtained about molecular motions, especially in chemistry and biology. The aim of this book is to provide a state of the art exposition of quasielastic neutron scattering both for specialists in this subject and for those who work in related fields such as NMR, infrared and Raman spectroscopy. Quasielastic Neutron Scattering starts with a thorough grounding in basic theory and then describes the instruments and methods used in cold neutron scattering such as neutron spin-echo spectrometers. They follow comprehensive treatments of multiple scattering techniques, long-range translational diffusion and molecular reorientations in orientationally disordered crystals. Recent developments in orientationally disordered phases are described, followed by the results of studies on single crystals and two-dimensional compounds. The investigation of continuous or random jump diffusion of molecules in bounded media is carefully explained. The final chapter describes dynamical studies of polymers and biomolecules. Quasielastic Neutron Scattering will be invaluable to both those research workers and postgraduates who specialise in neutron scattering and to those who are mainly interested in results.