Polarization-modulated Fourier transform infrared reflection-absorption spectroscopy (FT-IRRAS) is shown in this letter to be applicable to the study of the electrode/electrolyte interface. The technique provides good quality vibrational spectra of monolayers adsorbed at the electrode surface. The infrared spectra of CO adsorbed on a smooth platinum electrode in 1 N H/sub 2/SO/sub 4/ saturated with CO gas as a function of electrode potential are presented. 3 figures.