This book is intended for any student of physics who wants a thorough grounding in the quantum theory of nonrelativistic scattering. It is designed for a reader who is already familiar with the general principles of quantum mechanics (as taught, for example, in the first year graduate course at most American universities) and who has some small acquaintance with scattering theory, as would be acquired in the same first-year course. It is my hope to bring the student of atomic or nuclear physics to the point where he can begin reading the literature and tackling real problems, with a complete grasp of the underlying principles. For the student of high-energy physics I have tried to provide the necessary background for his later study of relativistic problems.