The kinetics of thermolysis of sucrose in solution in anhydrous dimethyl sulphoxide have been studied. The reaction appears to be facilitated by intramolecular hydrogen-bonding and is inhibited by intermolecular hydrogen-bonding to water or alcohols. The thermolysis yields α- d-glucopyranose (which then anomerises) and the fructofuranosyl carbonium ion which can react with benzyl alcohol to yield benzyl α- and β- d-fructofuranosides. This fructosyl cation is probably also the precursor for the formation of 2,6-anhydrofructofuranose in the thermolysis of sucrose.