The electrocapillary curve and temporal stability of the interfacial tension were measured for a polarized flat water-dichloroethane interface under electrochemical instability. The interfacial tension was measured on the basis of capillary wave spectra obtained by means of the heterodyne detection of the light scattered at the interface. Anomalous behavior of the electrocapillary curve was observed in the potential range in which the electrochemical instability was expected. The correlation between the interfacial tension and the current spike observed in the chronoamperometry was examined. Despite the presence of the anomalous current spikes and other phenomena showing thermodynamic instability, the results revealed that the interfacial tension was stable and did not show any correlation with the anomalous current. The results were explained by a structure formation by the lateral mass transfer to avoid the instability, in addition to the vertical interfacial ion transfer which is apparently observed by the current measurement. (c) 2006 Elsevier B.V. All rights reserved.