Several recent papers1–3 have discussed the origin of the sulphate aerosol in the stratosphere in terms of atmospheric carbonyl sulphide (OCS) and carbon disulphide (CS2). There is, however, considerable uncertainty in the life cycles and budgets of these compounds. This arises from a lack of knowledge of the various possible sources and also from the differences in the reported rate constants for the reactions of OCS and CS2 with hydroxyl (OH) radicals4,5, which provide a potentially large sink for these molecules in the troposphere. We report here measurements of rate constants and product formation for OH reaction with several sulphur compounds, including OCS and CS2. The results support the suggestion that oxidation of CS2 is a significant source of atmospheric OCS, but do not give conclusive evidence for a large sink for OCS in the troposphere.