Electrodeposition voltammograms are studied by Monte Carlo simulations when strong attractive interactions exist between the adsorbed atoms. The existence of a phase transition in the electrosorption isotherm leads to a nucleation and growth process when electroplating takes place for temperatures lower than the critical temperature for phase separation. In that case, we show that the voltammograms derived from the Monte Carlo simulations differ strongly from those obtained within the mean-field approach, particularly for low sweep rates. Thus, the potential, the asymmetry and, above all, the current density at the peak appearing in the voltammograms are widely overestimated in the mean-field approach. However, by using an approach based on the Kolmogorov-Johnson-Mehl-Avrami formalism and on a generalization of the classical nucleation theory, we are able to reproduce all the peak characteristics very well. Moreover, we show that they depend very little on temperature, contrary to what is obtained within the mean-field approximation. Furthermore, the divergence of the dimensionless current density as (1/v(b)) predicted by the mean-field approach for low sweep rates v(b) is substituted by a much slower divergence in (1/v(b))(2). (C) 2004 Elsevier B.V. All rights reserved.