This study aimed to identify the major odor contributing components produced during swine feces composting which have an impact on the olfactory senses. A total of 64 gas samples collected at different stages of composting were analyzed by both a gas chromatograph and human panel test using the triangle odor bag method. Multiple regression analysis of representative odor substances present in the outlet gas was carried out employing the odor index (OI) as the dependent variable and the odor unit as the independent variable. The recorded changes in OI indicated that turning was an important event during odor evolution, and that the odor emission during the thermophilic phase should be the main target for odor abatement. The model incorporating ammonia, methyl mercaptan and dimethyl sulfide as independent variables confirmed the value of the OI (R(2) = 0.70). These compounds were identified to be the key odor components significantly determining the OI. (C) 2009 Elsevier Ltd. All rights reserved.