The reaction between dimethyl sulfide (CH3SCH3) and nitrate radical (NO3) is studied using density functional theory and ab initio methods. The transition state for this reaction is optimized at different levels of theory and basis sets, and then used for kinetics calculations of the rate constant. The CH3SCH3 + NO3 reaction leading to CH3SCH, and HNO3 is shown to have a negative activation energy and thus negative temperature dependence. The study confirms that the NO3 radical is a significant contributor to the oxidation of DMS in the troposphere. (c) 2006 Elsevier B.V. All rights reserved.