The decolorization of orange II by the D.C. electrocoagulation (EC) method has been studied. In the EC of orange II, the effects of initial pH, rate of stirring, concentration of dye, electrodes distance, current density, water temperature, etc were tested. The optimum operating range for each of these operating variables was experimentally determined. The experimental results revealed that the color of orange II in aqueous phase was effectively removed ( > 98%) and also the chemical oxygen demand (COD) reduced ( > 84%), when iron was used as sacrificial anode and the concentration of orange II was < 200 ppm. The bach experimental results were assessed in terms of color and COD reduction. The optimum current density was 34.62 A/m(2) for effectively removing of orange II. The EC method is found to be quite effective in removing of orange II. This method can neutralize solution pH. In this project desorbed compounds are separated and structures of them are identified and another mechanism for removal of orange II is proposed. (C) 2002 Elsevier Science B.V. All rights reserved.