A calculation is made of the internal friction in GaP single crystals, produced by the reorientation of the divacancies of Ga atoms due to external stresses and the interaction between the vacancies. The ratio of the internal friction maxima in GaP, which correspond to the longitudinal oscillations in the [100] and [111] directions is found to be equal to 1.6, which is in good agreement with the results obtained experimentally for nondoped GaP single crystals with the help of the composite piezoelectrical oscillator method.