A method for the calculation of the electronic structure of interfaces is described and applied to the (100) Ge-GaAs and Ge-ZnSe heterojunctions. The method is based on the Koster-Slater scattering-theoretic technique. The interface is described as a local perturbation of an unperturbed system consisting of two initially noninteracting, lattice-matched bulk solids. The changes in their electronic structure due to the interface can be calculated very efficiently and accurately in terms of one-particle bulk Green's functions. We present interface band structures and wave-vector-integrated as well as wave-vector-resolved local densities of states for the Ge-GaAs and the Ge-ZnSe interfaces. All four interfaces give rise to essentially three interface bands in the valence-band region, those for Ge-ZnSe being more pronounced than those for Ge-GaAs. We compare our results with a previous calculation for the (100) Ge-Ga interface and with experiment. We conclude that stoichiometrically mixed interfaces are more likely to occur in nature than ideal (100) interfaces. © 1980 The American Physical Society.