The effect of pulsating flow on the mass transfer in an annular electrodialysis cell has been studied in terms of the, limiting current. The results indicate that the limiting current is influenced by the fluid velocity, the pulsation amplitude and the pulsation frequency, giving an increase of 400% with respect to the steady state. For a given amplitude, the dimensionless velocity, alpha(0) (alpha(0) = a omega/v), can be taken as a representative parameter of the pulsation effect on the mass transfer. The fractional increase in the Sherwood number in pulsating flow with respect to the steady state has been correlated in terms of the dimensionless velocity, alpha(0), and the Stokes number, alpha(1) (alpha(1) = D-eq(omega/v)(1/2)), giving the correlation : Sh(p)-Sh(0)/Sh(0) = 0.192(alpha(0) alpha(1))(0.377).