The influence of an alternating (AC) sinusoidal perturbation, of known frequency and small amplitude, superimposed to the usual applied continuous (DC) signal in a desalination electrodialysis process has been studied. The experiments were carried out with two types of ion-exchange membranes and sodium chloride aqueous solutions of two initial concentrations and at different frequencies of the AC signal. The results show that the presence of the AC perturbation favours the desalination process, mainly at the lowest frequencies. This fact is considered as a consequence of that the electroosmotic transport accompanying ion transfer during the process is affected by the AC perturbation. This behaviour suggests that the presence of an AC perturbation may influence on the efficacy of the desalination process.