Alkyl and aryl sulfides are oxidized to the corresponding sulfoxides or sulfones in excellent yields with aqueous hydrogen peroxide in the presence of silica sulfuric acid as an efficient solid acid catalyst. The oxidation of alkyl and aryl sulfide proceeds at 25-90 degrees C and the corresponding sulfoxides or sulfones was selectively obtained by controlling the amounts of H2O2 and catalyst. (C) 2006 Elsevier B.V. All rights reserved.