Studies of carbon monoxide oxidation on an Ag-25 at% Pd alloy electrode in a cell with a solid oxygen-conducting electrolyte -CO + O-2, Ag-Pd 0.9ZrO(2) + 0.1Y(2)O(3) Pt + PrO2-x, air-were carried out. XRD, SEM and XPS techniques were used for characterisation of the Ag-Pd alloy electrode. The non-Faradaic effect of electrochemical oxygen pumping on the rate of carbon monoxide oxidation was demonstrated. The induced change in the reaction rate at cathodic polarization of the Ag-Pd alloy electrode was an order of magnitude higher than the rate of oxygen pumping from the reaction zone through the electrolyte. The observed phenomenon was qualitatively explained on the base of a chain reaction mechanism involving electrochemically generated oxygen species.