Thin films of vanadium oxide were prepared by means of r.f, reactive sputtering. Their physical properties were studied as a function of the oxygen content in the sputtering atmosphere. Atomic force microscopy (AFM) and X-ray photoelectron spectromicroscopy (XPSM) investigations have been used for the study of the morphology and the chemical composition. In addition electrical characterisation in controlled atmosphere has been also performed for the evaluation of gas sensing properties, In particular, films deposited with 15% O-2 in the sputtering chamber were found to tx more resistive and to exhibit the best sensitivity when exposed to different gases. This behaviour has been explained taking into account the presence of different crystallographic phases and the influence of the polycrystalline nature of the films.