In this paper, the application of Fenton and Oxone/Co(2+) oxidation processes for landfill leachate treatment was investigated. The removal of the chemical oxygen demand (COD), suspended substances (SS) and the color of the landfill leachate by Fenton oxidation to that by Oxone/Co(2+) oxidation were compared under optimal operational conditions. For Fenton oxidation process, the optimal conditions were determined as: [H(2)O(2)]=80 mmol L(-1), [H(2)O(2)]/[Fe(2+)]=2.0, initial pH=2.5, reaction temperature=37.5+/-1 degrees C, reaction time=160 min, number of stepwise addition=3. Under the given conditions, 56.9% of the COD removal efficiency was achieved, but the SS and the color of the treated landfill leachate increased due to the generation of a large quantity of ferric hydroxide sludge. In reference to Oxone/Co(2+) oxidation process, the optimal conditions were determined as: [Oxone]=4.5 mmol L(-1), [Oxone]/[Co(2+)]=10(4), pH=6.5, reaction temperature=30+/-1 degrees C, reaction time=300 min, number of stepwise addition=7, the COD, SS and the color removal efficiencies were 57.5, 53.3 and 83.3%, respectively. From this work, it can be concluded that Oxone/Co(2+) oxidation process demonstrated higher degradation efficiencies of the COD, SS and color for landfill leachate treatment than that by Fenton oxidation process. It also suggested that Oxone/Co(2+) oxidation process could be considered as one of the most promising technologies for practical applicability to treat landfill leachate in large scale. For further improving the efficiency of Oxone/Co(2+) oxidation process, we proposed that combination of it with other technologies in future such as ultraviolet, ultrasound and biological methods.