Fundamental studies of the interaction of sulfur-containing molecules with titanium and vanadium oxide surfaces are of great importance given the widespread study and use of these materials as catalyst supports and the notorious nature of sulfur as a catalyst poison. We report here a detailed photoemission investigation of the interaction of SO2 with well-characterized single-crystal surfaces of TiO2, Ti2O3, and V2O3, and of H2S with well-characterized surfaces of TiO2. It is found that sulfur has a remarkable impact on the oxidation properties of these oxides. A complete oxidation of suboxides of Ti by exposure to SO2 has been observed using ultraviolet photoemission spectroscopy and x-ray photoemission spectroscopy; this is not possible by exposure to O2. TiS2 and TiO2 are formed at the Ti2O3(101̄2) surface following SO2 exposure. In contrast, the suboxide of V studied, V2O3, could not be significantly oxidized by exposure to SO2. Weak molecular and dissociative adsorption occurred, with the reaction saturating on a variety of different V2O3 surfaces for SO2 exposures <5 L. The reaction H2S with reduced TiO2(110) surfaces was also found to be weak, with an initial dissociative adsorption at exposures <10 L, followed by molecular adsorption. Exposure of the reduced surface to H2S passivates the surface, inhibiting O2 uptake.