Ru Al 2O 3 and RuMo Al 2O 3 catalysts have been prepared by impregnating respectively γ-Al 2O 3 and calcined Mo Al 2O 3 with aqueous solutions of ruthenium (III) acetate. XPS spectra of catalysts dried at 393 K, calcined in air at 873 K, and sulfided in H 2 H 2S are reported. Ru and Mo species in the catalysts, according to the respective binding energies, were ruthenium dioxide and oxomolybdenum (VI) in catalysts calcined at 873 K and a ruthenium sulfide and MoS 2 in the sulfided catalysts. Unusually low Ru binding energies were found for some catalysts. The properties of the catalysts in thiophene HDS are interpreted with the aid of the XPS results.