The hydrolysis of carbonyl sulphide over two alumina catalysts (surface areas 150 and 300 m(2) g(-1)) has been studied. Virtually all previous studies have focussed upon concentration ranges for the reactants ([COS] typically>1000 ppm) and temperatures (typicaIly>100 degrees C) that are much higher than those experienced in real industrial processes. In the study presented here. the concentration of carbonyl sulphide investigated is 150 ppm and temperatures in the range 30-250 degrees C are investigated. At higher temperature (250 degrees C) the data obtained are in agreement with previous studies and the reaction follows Langmuir-Hinshelwood kinetics with the surface hydrolysis of a thiocarbonate being the rate determining step. At lower temperatures (30-60 degrees C) the data indicate that the rate of COS hydrolysis decreases monotonically with increasing [H2O]. These data are consistent with Langmuir-Hinshelwood kinetics where the products are not adsorbed and either (a) the adsorption of COS is rate determining or (b) the surface reaction of adsorbed COS and an intermediate derived from H2O is rate determining. The current experiments cannot differentiate between these possibilities. Under these conditions it is the surface area of the alumina catalyst that is the important design parameter, a feature not observed in previous high temperature studies.