In this paper it is shown, for the first time, the presence of current oscillations in the electro-oxidation of carbon monoxide on a rotating platinum electrode. The current oscillations occur in a very restricted potential region around 950 mV vs. reversible hydrogen electrode, and may be observed for over 12 h. They are discussed in terms of the mechanism for CO electro-oxidation and the mutual influence of the processes of CO adsorption and formation of oxygenated species on the surface. (C) 2002 The Electrochemical Society.