Thin film fabrication techniques have opened a new era for many electronic devices. However, in the field of gas sensors, thin films have not reached their fully developed stages. In this study, the metal organic chemical vapor deposition (MOCVD) technique has been utilized for the deposition of tin oxide (SnO ) thin films on polished alumina (Al O ) substrates. For the purpose of the microstructure characterization of the films, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Auger electron spectroscopy (AES) have been applied. The films were subjected to sensing tests in both dry air and 1% H , balanced by dry air, environment in order to investigate their sensing behavior in relation with the microstructure. The films exhibited faceted grains with rough surface morphology and were composed of columnar grains with pore channels along the grains. The maximum sensitivity occurred between 450 and 500°C with a magnitude of approximately 20. © 1997 Elsevier Science S.A.