Kramer's Complex Band Structure Model, which has been used to describe optical properties of amorphous semiconductors, has been improved by introducing an effective pseudopotential that takes into account characteristic distortions of the short range order of tetrahedrally bonded semiconductors. Numerical results on Ge andGaAsyield a simple explanation why the two lowest valence bands coalesce in Si and Ge and do not inIII–V‐compounds.