The anaerobic treatability of malt whisky distillery wastewater was investigated. Biochemical methane potential (BMP) experiments were conducted both with and without basal medium (BM) to observe the effect of nutrient supplementation. For batch reactors containing no nutrients but only NaHCO3, net total gas production at the end of 29 days were observed as 0.019 m(3) gas/kg COD removed. With nutrient supplemented reactors the net total gas production was 0.020 m(3) gas/kg COD. Continuous reactor experiments were carried out in two stage upflow anaerobic sludge blanket (UASB) reactors. These experiments indicated that the two stage UASB reactor configuration is an efficient system for malt whisky wastewater treatment until up to 33 866 mg/l influent COD concentration. Following the UASB experiments aerobic experiments in batch reactors were also conducted and further COD and BOD removal of up to 55 and 70%, respectively, were achieved. (C) 2003 Elsevier Science Ltd. All rights reserved.