The uncatalysed aqueous oxidation of S0 2 is a reaction with diverse applications, and it has long been the subject of considerable controversy. The extensive literature on this reaction is critically reviewed and the results of kinetic studies are presented in tabular form. A number of factors which may be responsible for the discrepancy between reported experiments are discussed, and of these the pH and the purity of experimental solutions appear to be the most important. The following rate equation is proposed for predicting atmospheric oxidation rates via this reaction:The mechanism appears to be of little consequence in the conversion of atmospheric SO 2 .