The electrophoretic behavior of a concentrated spherical dispersion under an applied alternating electric field is investigated theoretically. We consider the case of low surface potential and the arbitrary thickness of the double layer, and the interaction between neighboring double layers may be significant. The boundary condition of the cell model of Shilov and Zharkikh (Colloid J. 1981, 43, 434) is adopted, which improves the performance of that used by Levine and Neale (J. Colloid Interface Sci. 1974, 47, 520). The difference between the magnitude of electrophoretic mobility based on these two cell models is found to increase with the volume fraction of particle; the phase lag, however, is the same regardless of which cell model is used. We show that the mobility decreases with an increase in the frequency of the applied electric field; the smaller the particle is the more sensitive the variation of the mobility to the frequency will be. The limiting mobility as double layer becomes infinitely thin depends on both the frequency of the applied electric field and the volume fraction of particles.