The use of periodic current signals (square, triangular, Dirac delta pulse, sinusoidal and displaced square waves) of very low frequencies and amplitudes has been investigated for the evaluation of the real surface area of electrodes. The potential response of an electrode perturbed with any of these signals, which produce a small departure from the equilibrium condition, allows us to evaluate the polarisation resistance and the interfacial capacity. The real electrode area can be accurately determined from both values, especially from the last one. A procedure for the analysis of the transient response and for the evaluation of the accuracy of the proposed method, based on the application of parallel RC circuits, is also given.