The photodecolorization of the azo dye Direct Orange 34 (DO34) was investigated in TiO 2 aqueous suspensions with artificial irradiation at 30ºC. The experimental conditions were optimized by a 2 5 factorial design, using the decolorization percentage after 240 min irradiation as the response. The five factors considered were DO34 and TiO 2 concentrations, stirring speed, air saturation, and adsorption time. The addition of hydrogen peroxide and sodium periodate as oxidants increased the decolorization rate.