The homogeneous metal/bromide-catalyzed aerobic oxidation of p-xylene with different catalyst concentrations was carried out, and the formation kinetics of COx including CO2 and CO was measured. The simplified elementary steps for the formation of COx were summarized, on the basis of which the kinetic model of COx formation was established. The model calculations were in good agreement with the experimental data for the CO2 formation and also successfully captured the first peak of the CO formation rate as a function of time. The obtained rate constants have narrow confidence intervals, among which only k1 and k2 are the adjustable parameters for different catalyst conditions. The decarboxylation of the carboxyl group in aromatic acid, the oxidation of the aryl radical, and the destruction of acetic acid are the major sources of CO2. The formation of CO mainly results from the destruction of acetic acid and the oxidation of the aryl radical. © 2012 Wiley Periodicals, Inc. Int J Chem Kinet 44: 277–283, 2012