The oxidation of CH3OH on V2O5 has been studied from room temperature to 250 degrees C. The reaction products were analyzed by on-line gas chromatography (GC) and the adsorbed species were characterized by "in situ" diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS). Both isothermal and non-isothermal experiments were carried out in order to identify adsorbed species in the oxidation of CH3OH on V2O5 catalysts, The interaction of CH,OH with the V2O5 surface results in the formation of methoxy groups and V-OH species as stated by DRIFTS. The infrared spectra suggest that more than one catalytic site are involved in the adsorption process. The formation of V-OH and the resulting reduction of the vanadia catalyst leading to V4+-O and V3+ groups is inferred from DRIFTS data and X-ray diffraction patterns of the used catalysts showing the presence of reduced oxide phases. As the reaction proceeds, the adsorbed methoxy species are oxidized to H2CO, formate species, partial oxidation products, CO and CO2.