The effects of UV light illumination on the performance of SnO2 and In2O3 semiconductor gas sensors toward CO and NO2 are reported. The sample were prepared with DC sputtering in Ar atmospheres by the Rheotaxial Growth and Thermal Oxidation (RGTO) technique and with reactive magnetron sputtering in Ar and O-2 atmosphere, respectively. Results are quite promising for the development of sensor working at room temperature. (C) 2000 Elsevier Science S.A. All rights reserved.