New experimental results were obtained for the oxidation of o-xylene studied in a jet-stirred reactor (JSR) at atmospheric pressure in dilute conditions over the temperature range 900-1400 K, and variable equivalence ratio (0.5 ≤ φ ≤ 1.5). The data consisted of concentration profiles vs. temperature of the reactants, stable intermediates and final products, measured by sonic probe sampling followed by on-line GC-MS analyses and off-line GC-TCD-FID and GC-MS analyses. The ignition of o-xylene-oxygen-argon mixtures was measured behind reflected shock waves over the temperature range 1400-1830 K, at 1 atm, and variable equivalence ratio (0.5 ≤ φ ≤ 2.0), using a shock tube (ST). The oxidation and ignition of o-xylene under respectively JSR and ST conditions were modeled using a detailed chemical kinetic reaction mechanism (189 species and 1359 reactions, most of them reversible) deriving from a previous scheme proposed for the ignition, oxidation, and combustion of simple aromatics (benzene, toluene, styrene, n-propyl-benzene, m-xylene, and p-xylene). Sensitivity analyses and reaction path analyses, based on rates of reaction, were used to interpret the results. This study showed the reactivity of o-xylene is higher than that of m-xylene and p-xylene under the present.