Vertically aligned ZnO nanorods were grown on flexible polyimide films by a thermolysis assisted chemical solution method to fabricate an ethanol sensing material. Flexible ZnO nanorod sensors were examined to monitor ethanol gas by varying the working temperature from 300 to 125 degrees C and by changing the ethanol concentration in a range from 100 to 10 ppm in synthetic air. A flexible ZnO nanorod sensor can detect 100 ppm of ethanol gas with a sensitivity of 3.11 at 300 degrees C. When compared with ZnO nanorod sensors fabricated on a silicon dioxide hard substrate, its sensing performance exhibited competitive sensitivity. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3479692] All rights reserved.