A model for the catalytic (EC') mechanism on the three-phase electrode arrangement is developed. It is assumed that a solid electrode surface is partly covered by an insulating solution of substance A in an organic liquid which is immiscible with water and immersed into an aqueous solution of a depolarizer and a supporting electrolyte. At the liquid/liquid interface the substance A reacts with the aqueous phase product of the electrode reaction occurring at the uncovered parts of the electrode with regeneration of the depolarizer. An average cyclic voltammetry response, a distribution of the current density and a pure kinetic current are calculated using a finite difference method. (C) 2004 Elsevier Ltd. All rights reserved.