The adsorption and reaction of methanol (CH3OH) on stoichiometric (TiO2-terminated) and reduced SrTiO3-(100) surfaces have been investigated using temperature-programmed desorption (TPD), X-ray photoelectron spectroscopy (XPS), and first-principles density-functional calculations. Methanol adsorbs mostly nondissociatively on the stoichiometric SrTiO3(100) Surface that contains predominately Till cations. Desorption of a monolayer methanol from the stoichiometric surface is observed at similar to 250 K, whereas desorption of a multilayer methanol is found to occur at similar to 140 K. Theoretical calculations predict weak adsorption of methanol on TiO2-terminated SrTiO3(100) surfaces, in agreement with the experimental results. However, the reduced SrTiO3(100) surface containing Ti3+ cations exhibits higher reactivity toward adsorbed methanol, and H-2, CH4, and CO are the major decomposition products. The surface defects on the reduced SrTiO3(100) surface are partially reoxidized upon saturation exposure of CH3OH onto this surface at 300 K.