A solution supersaturated with hydrogen around a platinum wire electrode was studied by double-potential step chronoamperometry. The time-current curve at the hydrogen oxidation potential obtained with double-potential step increased with a shift of the hydrogen evolution potential to the cathodic potential. The initial slope of the chronoamperogram at the oxidation potential increased to zero with the shift from the hydrogen evolution potential to the cathodic potential. The increase was observed with increasing ionic strength and increasing cathodic current density. These phenomena were analyzed with numerical method using a number of assumptions. (c) 2006 Elsevier Ltd. All rights reserved.