The voltammetric behaviour of rhodized electrodes (roughness factor values, 15-25) was studied in 1 mol dm(-3) H2SO4 solution in the potential range from 225 to 500 mV/RHE. It was shown that, at appropriately chosen sweep rates and at high current-measuring sensitivities, characteristic voltammograms with a singular point (minimum) could be obtained. Addition of strongly adsorbing chloride ions significantly modifies the picture : the singular point disappears and double-layer-like behaviour can be observed. The phenomena observed are treated and explained in terms of simultaneous adsorption of H and OH species.