The electrochemical oxidation of aqueous wastes polluted with benzoic and salicylic acids and phthalic anhydride on boron-doped diamond electrodes has been studied. The complete mineralization of the organic waste has been obtained in each case regardless of the nature of the compound, composition of the solution, and current density. Different voltammetric behaviors between benzoic acid, salicylic acid, and phthalic anhydride were obtained in the voltammetric study, but no differences in the electrochemical oxidation of the three compounds seems to exist in the bulk electrolyses study. The total mineralization of the three compounds at different current densities confirms that the oxidation must occur directly on the electrode surface and/or by hydroxyl radicals generated by decomposition of water and/or by other oxidants electro-generated from the sulfate oxidation.