Isopotential points in reverse square-wave voltammetry of irreversible electrode reactions are described for the first time. Experimental results (obtained with Eu3+ in Perchlorate solutions) and model calculations indicate that such an intersection appears when the net signals, recorded at increasing step potential, are plotted together. As long as the transfer coefficient is equal to 0.5, the isopoint appears at the standard potential Eo, irrespective of the kinetic parameter K. Otherwise, it is shifted positively or negatively. The effect could be used for determination of the standard potential, recognition of symmetric/asymmetric processes and testing the quality of experimental data. (C) 2009 Elsevier B.V. All rights reserved.