The temperature dependence of the CO desorption process on a carbon-supported platinum-ruthenium alloy catalyst has been investigated using isotopic exchange experiments. The kinetics of CO desorption on PtRu/C catalyst have been studied as a function of temperature and flow rate. Desorption rate constants have been determined for a temperature range between 25 degrees C and 150 degrees C. All PtRu/C results have been compared with those obtained for the Pt/C catalyst under similar experimental conditions. Quite different desorption rate constants have been observed. The variation in apparent Arrhenius parameters (frequency factor A and activation energy E-a) for PtRu/C and Pt/C could possibly explain their different degrees of poisoning by CO in proton exchange membrane fuel cells (PEMFCs) and the underlying adsorption/desorption processes. The effect of temperature treatment on the PtRu/C catalyst properties has also been investigated with respect to CO desorption kinetics and to the associated microstructural transformations. (C) 2009 Elsevier Inc. All rights reserved.