ZnO sensors were fabricated from ZnO tetrapod structures prepared in four different atmospheres and their gas-sensing properties were investigated. It was found that the gas-sensing properties were strongly dependent on the preparation atmosphere. This is likely due to the effects of the preparation atmosphere on the intrinsic defect concentration. It was found that the sensors based on tetrapods prepared in humidified Ar flow exhibited the best performance, characterized by high response, good selectivity and very short response time to dilute C2H5OH, making them promising candidates for practical detectors for dilute C2H5OH. (C) 2004 Elsevier B.V. All rights reserved.