The kinetics of the oxidation of natural gas blends (CH4/C3H8and CH4/C2H6/C3H8) has been studied in a jet stirred reactor (900 < T/K < 1230, 1 < P/atm < 10, 0.1 < equivalence ratio < 1.5). Mole fractions of reactants, intermediates and products have been measured in a JSR as a function of temperature and mean residence time. These results have been used to validate a detailed kinetic reaction mechanism. Literature ignition delay times of CH4/C3H8/O2mixtures measured in shock tube have also been modeled. A general good agreement between the data and the model is found. The same mechanism has also been used to sucessfully represent the oxidation of methane, ethyne, ethene, ethane, propene, and propane in various conditions including JSR, shock tube and flame. The present study clearly shows the importance of traces of ethane and propane on the oxidation of methane. The computations indicate that the oxidation of methane is initiated by its reaction with O2and by thermal dissociation when no other hydrocarbon is present. In CH4/C3H8/O2and/or C2H6mixtures, ethane and propane react first leading to the formation of OH, H and O radicals which initiate methane oxidation.