The wet air oxidation of aqueous solutions of aniline over a Ru/CeO2 catalyst was investigated. Batch oxidation experiments were performed at temperatures between 160 and 230degreesC and an oxygen partial pressure of 2 MPa. Liquid phase reaction intermediates were identified and their concentration time profiles were followed by means of high-performance liquid chromatography. Gas chromatography was also used to follow the concentration of carbon dioxide formed; therefore the extent of total oxidation that had occurred was measured. Based on the experimentally determined reaction intermediates a reaction mechanism for the oxidation of aniline was proposed. In addition a computational approach based upon thermodynamics was used to determine possible reaction pathways. It appears that the theoretical and experimental approaches are in good agreement and provide complementary information that can be used for refining reaction pathways.