Thin copper-doped SnO2 films have been shown to exhibit sensitivity to PH3 in the region of its threshold limit concentrations in air. The films were deposited by spraying alcohol solutions of SnCl4 and CuCl2 over hot quartz substrates with subsequent annealing in an oxygen atmosphere at high temperatures. The phase and chemical composition of the films were investigated, using X-ray phase and electron diffraction analyses and X-ray photoemission spectral and Auger emission spectral analyses. The gas sensitivity was estimated by the change in the electrical resistance of the film in the absence and in the presence of PH3. The films prepared by spraying working solutions with molar ratio CuCl2:SnCl4 = 1:4 exhibit the highest sensitivity towards 0.1 ppmn PH3 (Rair/Rgas = 15.5) at 170°C. At this temperature the selectivity with respect to hydrogen is at its highest. © 1992.