The feasibility of a large scale application of the light-enhanced Fenton reaction has been investigated for the treatment of a highly contaminated industrial waste water containing toxic aromatic amines (dimethyl anilines or xylidines) as the main pollutants. The Fenton reagent, a combination of hydrogen peroxide and a ferrous salt, is a potent oxidizing agent of organic compounds in acidic aqueous solution, and UV/visible irradiation may significantly enhance the degradation rates. Preliminary laboratory rests on the model compounds, 2,4- and 3,4-xylidine have been performed for selecting appropriate experimental conditions. Subsequent experimentation on the industrial waste water at a large scale level (3000 mg Cl-1, 500 l) has been carried out using an experimental design methodology for the simulation and the evaluation of the effects of the two critical factors, hydrogen peroxide and ferrous ion concentrations. The results indicate that the light-enhanced Fenton reaction is a most effective treatment process under acidic conditions and is a realistic alternative to adsorption of xylidines on activated carbon as used at present.