The catalytic ozonation of oxalic acid in a batch reactor using TiO 2, MnO2/TiO2 and Rh/TiO2 as catalysts was studied. The presence of the catalyst significantly improves the ozonation rate in comparison with the noncatalytic reaction. The adsorption and the extent of degradation of oxalic acid were found to be dependent on the solution's pH. Higher degradation rates were found for catalytic systems at pH 2.5, where the oxalic acid concentration in the water phase was almost completely removed. The contribution of the MnO2/TiO2 and Rh/TiO2 catalysts as well the TiO2 support is discussed. The highest mineralization, expressed as CO2 evolution, was reached with the MnO2/TiO2 catalyst at pH 2.5. © 2007 Sociedad Chilena de Química.