This study describes extraction of selected volatile fatty acids (VFAs) (containing from 2 up to 8 carbon atoms) with methyl-tert-butyl ether (MTBE) from polluted aqueous samples followed by separation, identification and quantification by gas chromatography coupled with mass spectrometry (GC-MS). Extraction parameters such as time and number of extractions, volume ratio, effect of acidification and salt addition were optimized with respect to recovery, enrichment factor and repeatability. The VFAs studied were separated using an open tubular capillary column Stabilwax-DA (crossbond polyethylene glycol treated with nitroterephtalic acid). The limits of quantitation (LOQ) of the procedure developed were on the level of 0.1 to 0.5 mg L(-1). The analysis of real samples of municipal raw and treated wastewater, animal farms wastewater, and also landfill leachates showed that always dominant was acetic acid. The content of VFAs in animal farms wastewater was a few times higher than in municipal wastewater and in municipal solid waste landfill leachates. In surface and ground water close to municipal landfill only acetic acid was detected at higher concentrations in outflow than inflow water. This indicates that slight leakage from the landfill must have occurred.