The reliability and lifetime distribution of the indirect-heating gas sensors used for detecting C2H5OH are investigated in this paper. The reliability and the operation-lifetime test are carried out in the way that is the same with other electronic devices. During the long-time operation-lifetime test for over 125 days, the drifts in the sensitivity, selectivity, resistance, and response and recovery time of the sensors are obtained. Through the numerical analysis and data processing of the failure data, the lifetime distribution, distribution parameters, and reliability level are obtained. The curve of the lifetime distribution is the logarithmic normal distribution, and the mean lifetime is 11572 h. The results indicate that the gas sensors have good stability and reliability. They are important for the practical applications and the improvements of the gas sensors performance. (C) 2002 Elsevier Science Ltd. All rights reserved.