Linear electro‐optic effects in zincblende semiconductors are theoretically analyzed by means of a microscopic simple model without any fitting of parameters. Faust–Henry, second harmonic generation, and linear electro‐optic coefficients are obtained from the calculation of the derivatives of the susceptibility with respect to electric fields and ionic displacements. Our results for GaP, GaAs, InP, ZnSe, and ZnTe are in satisfactory agreement with the available experimental information.