New experimental results were obtained for the mutual sensitization of the oxidation of NO and methane in a fused silica jet-stirred reactor operating at 1-10 atm, over the temperature range 800-1150 K. Probe sampling followed by on-line FTIR analyses and off-line GC-TCD/FID analyses allowed the measurement of concentration profiles for the reactants, stable intermediates, and final products. Detailed chemical kinetic modeling of the experiments was performed. An overall reasonable agreement between the present data and modeling was obtained, whereas previously published models failed to properly represent these new data. According to the proposed model. the mutual sensitization of the oxidation of methane and NO proceeds through the NO to NO2 conversion by HO2 and CH3O2. The modeling showed that at 1-10 atm, the conversion of NO to NO2 by CH3O2, is more important at low temperatures (800 K) than at higher temperatures (850-900 K), where the reaction of NO with HO2 dominates the production of NO2. The NO to NO2 conversion is enhanced by the production of HO2 and CH3O2 radicals from the oxidation of the fuel. The production of OH resulting from the oxidation of NO promotes the oxidation of the fuel: NO + HO2 reversible arrow OH + NO2 is followed by OH + CH4 reversible arrow CH3. At low temperature, the reaction further proceeds via CH3 + O-2 reversible arrow CH3O2, CH3O2 + NO reversible arrow CH3O + NO2. At higher temperatures, the production of CH3O involves NO2: CH3 + NO2 reversible arrow CH3O. The sequence is followed by CH3O reversible arrow CH2O + H, CH2O + OH reversible arrow HCO, HCO + O-2 reversible arrow HO2, and H + O-2 reversible arrow HO2. reversible arrow CH2O + H, CH2O + OH reversible arrow HCO, HCO + O-2 reversible arrow HO2 and H + O-2 reversible arrow HO2. (c) 2004 The Combustion Institute. Published by Elsevier Inc. All rights reserved.