The wet air oxidation of long-chain carboxylic acids has been studied. Caprylic acid and oleic acid were selected for the degradation studies. The effectiveness of the process has been followed in terms of the disappearance of carboxylic acids and in terms of COD removal. The oxidation process was studied in the temperature range 473-573 K with a total pressure of 15 MPa of synthetic air, which means an oxygen excess. The oxidation process was found to be pseudo-first order with respect to the carboxylic acid concentration and the activation energies were 55.5 kJ/mol for caprylic acid and 53.8 kJ/mol for oleic acid. Acetic acid was found to be the main intermediate in the oxidation process and, therefore, a generalized kinetic model based on the formation and elimination of acetic acid has also been applied to the experimental data. (C) 2004 Elsevier B.V. All fights reserved.