The solution of the low-energy electron diffraction (LEED) problem at a crystal-vacuum interface by the layer-KKR method is shown to apply readily to transmission and reflection of electrons at crystal-crystal interfaces. A simple model of the scattering potential is described, which can be readily constructed for any configuration of atoms. The LEED spectra it yields are shown to give good agreement with experiment for several simple metals, when the effects of electron absorption and lattice motion are included. It is shown that LEED probes the first few surface layers of a crystal and is sensitive to changes in these layers, including parallel and perpendicular displacements of the first layer. Thus it is concluded that, in conjunction with multiple scattering calculations as described above, LEED is potentially a valuable tool for the determination of the structures of these layers. © 1972.