Nanoparticles of chromium oxide have been synthesized following a precipitation technique at reaction temperatures 5, 27 and 65 degrees C. Synthesized powders were characterized using X-ray diffraction, transmission electron microscope and Brunauer-Emmett-Teller techniques to carry out structural and morphological analysis. The reaction temperature has been found to be playing a crucial role in controlling particle size. It has been observed that Cr2O3 nanoparticles synthesized at 27 degrees C were smaller as compared to those synthesized at 5 and 65 degrees C. Chromium oxide samples thus prepared were deposited as thick films on alumina substrates to act as gas sensors and their sensing response to ethanol vapour was investigated at different operable temperatures. It has been observed that all the sensors exhibited optimum response at 250 degrees C. The investigations revealed that sensing response of Cr2O3 nanoparticles synthesized at 27 degrees C was exceptionally higher than that of Cr2O3 nanoparticles synthesized at Sand 65 degrees C. (c) 2012 Elsevier Ltd. All rights reserved.