Abstract: The band structures of ten semiconductors of A,ABand AB₂ types have been calculated by LCBO MO method. The results showed that the band gaps Eg can generally be expressed as a linear function of the bond energy and the resonance integrals between the neighbouring bonds, irrespective of the covalent structural types of the semiconductors. This provides a theoretical background for the empirical expressions between Eg and some properties of the chemical bonds reported in the literature.