Ozone in the presence of hydrogen peroxide has been employed succesfully for the oxidative degradation of polycarboxylic and diphosphonic acid chelating agents present at the 0.1 M level in a neutral or weakly alkaline aqueous solution. The geminal diphosphonic acid complexants methanediphosphonic acid and (1-hydroxyethylidene)bisphosphonic acid have been successfully mineralized, as have the polycarboxylic acids ethylenediaminetetraacetic acid and tetrahydrofurantetracarboxylic acid.