Deposition of tin monoxide thin films by reactive magnetron sputtering is investigated. The analysis by XRD and XPS have proved the presence of SnO as the main compound in the layers, which also contain SnO2 and metallic Sn. A set of process parameters for the obtention of these films is found. The material, used as sensitive layer in resistive type gas sensor, shows an increase in its resistivity when exposed to vapours of ethanol (p-type conductivity). (C) 2000 Elsevier Science Ltd. All rights reserved.