The technique of in-situ electrochemical Fourier transform IR spectroscopy has been extended to the study of a real carbon-supported platinum + ruthenium catalyst. Results are presented for the electro-oxidation of methanol at bulk Pt, Pt particles and carbon-black-supported Pt + Ru electrodes. Marked differences are observed, particularly with regard to the nature of the adsorbed CO species. Additional electrochemical mass spectrometry data support the suggestion made in a previous paper that the migration of CO to the surface is an important part of the reaction mechanism.