The curves (V, I) of different ion-exchange membranes have been determined under different experimental conditions. Taking into account the classical theory of concentration polarization, a method has been developed to adjust the (V, I) data, up to a certain value of I, which permits us to obtain easily the value of the limiting current density, I-L, in every experimental situation. From these values, the dependence of the limiting current density of the membranes used on the concentration and stirring rate of the solutions has been studied. To check the reliability of the method, the values of I-L thus obtained have been compared with those obtained by the usual methods; the similitude between both values is high.