We investigated tungsten monocarbide (WC) and Pt-modified WC as CO-tolerant electrocatalysts as compared to pure Pt. The binding energy of CO, estimated using temperature-programmed desorption, is weaker on WC and Pt/WC than on Pt, suggesting that it should be easier to oxidize CO on WC and Pt/WC. This hypothesis was verified using cyclic voltammetry to compare the electro-oxidation of CO on WC, Pt/WC, and Pt supported on carbon substrates, which showed a lower voltage for the onset of oxidation of CO on WC and Pt/WC than on Pt. (c) 2008 The Electrochemical Society.