This paper overviews the uses of scattering theory in physical chemistry, with emphasis on bimolecular chemical reactions. The topic is introduced with a historical survey of theoretical work on the H + H-2 reaction. Then several of the most commonly used methods are described, including time independent and time-dependent quantum methods, approximate quantum methods, and semiclassical and classical methods. The applications of these methods to three benchmark atom-diatom reactions, F + H-2, I + HI, and H + O-2, are considered in detail. These and the H + H-2 application are used to illustrate dynamical phenomena that are important in chemical processes, including tunneling, trapped state resonances, quantized transition states, energy partitioning, angular distributions, and geometric phase effects. Connections with molecular beam, photodetachment, and laser chemistry experiments are discussed. Other scattering theory applications, including electronically nonadiabatic reactions, reactions with four or more atoms, photodissociation processes, and condensed phase and surface reactions, are briefly mentioned.