Cyclic voltammetry and in situ infrared spectroelectrochemistry were employed to study the ionic adsorption on the Ag(111) electrode surface in sulfate-containing solutions of different pH. It has been concluded that the sulfate anion is the predominant species adsorbed at the electrode surface in acidic and neutral medium. The adsorption of sulfate in alkaline solutions is inhibited by the more strongly specifically adsorbed OH- ions. The potential dependence of surface coverage, estimated on the basis of spectroelectrochemical data, indicates that a considerable repulsion exists among the adsorbed sulfate species. The spectral data were compared to those obtained for sulfate adsorption on Pt(lll) and on underpotentially deposited Ag on the Pt(111) surface.