Changes in the resistivity of polycrystalline V-doped TiO2 upon exposure to SO2 in air allow application of the material as a sensor for detection of this important pollutant. Optimal sensitivity to SO2 is achieved at low doping levels, where there is also good selectivity relative to CO and CH4. Concentration of SO2 as low as 10 ppm produce a 10% change in the resistance of 0.5% V-doped TiO2, allowing facile detection of the gas at this level. Analysis of the kinetics of the resistance changes for 1% V-doped TiO2 as a function of temperature shows that the rate of initial response is only weakly activated.