Carbon-supported platinum and iridium catalysts were prepared for catalytic wet air oxidation (CWAO) applications. These catalysts were tested in the CWAO of butyric acid aqueous solutions at 200 degreesC and 6.9 bar of oxygen partial pressure, and significant conversions above 70% were obtained depending on the catalyst used. The long-term deactivation resistance of the PVC catalyst is higher than that of the Ir/C catalyst. The deactivation observed with the Ir/C catalyst was attributed to the overoxidation of the surface of iridium by molecular oxygen. A deactivation study of the catalysts was conducted using N-2 adsorption, thermogravimetric analysis, temperature-programmed reduction, and X-ray photoelectron spectroscopy. A kinetic model describing the observed deactivation phenomena in the Ir/C catalyst is proposed and tested using the experimental data obtained in the CWAO of the systems studied.