A theory of force constant models is derived for tetrahedral semiconductors from Harrison’s [Phys. Rev. B27, 3592 (1983)] tight‐binding theory. A relation between the three independent elastic constants is derived that is independent of the detailed form of the matrix elements. This relation provides an approximate, butabinitio, theory on which two‐parameter force constant models can be based. The universal matrix elements of Harrison are also found to describe remarkably well the magnitude of the elastic constants and their scaling from one material to another. Analytic forms forc11andc44are given in terms of the matrix elements.