The ZnO nanowires have been prepared and studied as the sensing element for the detection of ammonia. The ZnO nanowires were first synthesized by evaporating high purity zinc pellets at 900 degrees C and then distributed onto the electrode surfaces of quartz crystals at room temperatures. Gas sensitive properties of ZnO nanowires layer were studied in terms of the quartz crystal microbalance (QCM) at room temperature. It is found that the obtained response of the sensors varied with the thickness of the ZnO nanowires layer. ZnO nanowires showed high sensitivity to ammonia in the range of 40-1000 ppm. The response time of the sensor was as fast as similar to 5 s at any concentration (40-1000 ppm) of ammonia gas. The ZnO nanowires-coated sensors have a good frequency stability and reproducibility. All results demonstrated that the ZnO nanowire was a potential gas sensing material for practical use. (c) 2005 Elsevier B.V. All rights reserved.