Thin films of stannous tungstate have been grown by reactive co-sputtering in an 11% O2/Ar atmosphere where a tungsten target is operated in the r.f. mode and a tin target in the d.c. mode. The deposited amorphous films are annealed for 4 h at 400 or 600 °C in order to crystallize the films. XRD together with RBS, EDS and CEMS measurements are used for the characterization of the films. The films sputtered with 150 W power for both modes are found to have crystalline α-SnWO4 structure after annealing at 400 °C. CEMS results show that tin is in a divalent form (Sn2+) in α-SnWO4 films. The electrical resistivity together with the gas-response properties to different gases of the α-SnWO4 films have been measured at different temperatures between room temperature and 400 °C. In the case of response to CO and NO in air, an unusual dual-conductance behaviour is found. For comparison, measurements have also been made with a pure WO3 film and with some SnxWOy films having lower tin concentrations (x<1). © 1995.