TiO 2 /SnO 2 composites prepared by mechanical mixing of TiO 2 and SnO 2 nanopowders over a full compositional range from 100 mol% TiO 2 to 100 mol% SnO 2 are characterized by BET adsorption, isotherms method, X-ray diffraction, Scanning Electron Microscopy, SEM, Transmission Electron Microscopy, TEM, spectrophotometry and impedance spectroscopy, IS. Gas sensors made of these nanopowders show high and reproducible responses in reaction with hydrogen at a relatively low temperature, not exceeding 400°C. Remarkable increase in the sensor sensitivity accompanies mixing of SnO 2 nanopowder with a small amount (2 mol%) of TiO 2 . This effect can be accounted for by an enhanced oxygen preadsorption on SnO 2 grains due to the electron transfer from TiO 2 to SnO 2 .