Hydrodynamics and mass transfer in an annular electrodialysis cell with pulsed flow have been studied. Velocities were obtained solving the momentum equations, in the annular space between two concentric cylinders. The instantaneous velocity can be broken down into two components : a steady component with a parabolic profile, and an oscillatory component which presents two maxima in the nearby of the cylinder walls. The fundamental dimensionless groups that describe the velocity profiles are the Reynolds number, Re = nu D-eq/nu, the dimensionless velocity, alpha(0) = alpha omega/nu, and the pulse Reynolds number, alpha(1) = D-eq(omega/nu)(1/2). Mass transfer through the membrane was investigated in terms of the limiting current. For a given value of alpha(0), frequency has a more significant effect on the limiting current than amplitude.