The basic formulations of nonreactive scattering are presented in the sections to follow. The quantal approach to this problem is outlined. Specific symmetries, and their closely related conservation laws, which reduce the complexity of computation, are discussed, along with the usual coordinate systems used to express the necessary scattering equations. The derivation of the matrix elements needed for a given calculation is provided in the case of a diatom-diatom collision. Semiclassical and quasi-classical methods are also briefly introduced. The chapter ends with a comparison between theory and experiment for the benchmark CO–H2 system and an outline of future directions in the field. © 2023, Springer Nature Switzerland AG.