The anaerobic treatment of pot ale, a liquid waste-product from the malt whisky industry, was investigated at laboratory scale using UASB (upflow anaerobic sludge blanket) reactors. Chemical oxygen demand reductions of around 90% were achieved after dilution, pH adjustment and settlement of the pot ale. Large amounts of ammonia were produced during treatment and the pH of the waste rose significantly. The maximum space loading rate consistent with stable operation was around 15 kg COD/m(3) per day at a retention time of 2.1 days; higher loading rates produced process instability and failure. Extensive sludge granulation was observed during periods of stable operation.