Offensive odours which evolve during the decomposition of swine waste have resulted in complaints from neighbours in agricultural areas. This study chronologically monitored the emissions of volatile fatty acids (VFAs) during composting to quantify the release of malodorous compounds. Swine waste/sawdust mixtures and sawdust control were placed in 208 litre reactor vessels and constantly aerated over a 21-day period. Swine manure was collected at the Agricultural Technical Institute-The Ohio State University (Wooster, Ohio, USA) from 19-23 November 1998. Acetic, propionic, isobutyric, butyric, isovaleric and valeric acids were quantified in total collections of condensed water vapour and volatiles released from the vessels. Exit gases were passed through water-cooled condensers, and condensate was collected every 12 hours. Composting conditions were shown to be adequate by measuring carbon to nitrogen ratios, pH, temperature and moisture contents. The 21-day aerobic treatment decreased all VFAs in the swine waste mixtures by 61 to 100 per cent, with a mean of 87 per cent. Prior to peak gas volatilization, when the vessel contents attained peak composting temperatures, acetic acid was emitted in the greatest amounts, followed by butyric, propionic, valeric, isovaleric and isobutyric acids in order of decreasing emissions. Following peak gas volatilization, butyric acid was released in the greatest amounts, followed by acetic, propionic, valeric, isovaleric and isobutyric acids. The described condensation procedure was shown to be an effective method to quantify malodorous compounds emitted during the decomposition of livestock waste. In addition, aeration was an effective treatment to decrease VFAs and, therefore, odour potential resulting from their emissions.