To utilize a closed municipal solid waste landfill site in environmentally secure conditions, itis necessary to verify the stabilization level of landfill leachate. To assess leachate stabilization ofan open-dumping municipal solid waste landfill site (Salmi Landfill) which is located at thevicinity of Chungju Reservoir which flows into Paldang Reservoir utilized as SeoulMetropolitan water supplies, the landfill history and surrounding characteristics of the landfillsite were surveyed.In this investigation, waste, leachate, groundwater and surfacewater samples from thislandfill were physically and chemically analyzed, and the analysis results were evaluated by‘The Criteria of Landfill Waste Stabilization (CLWS)’, ‘Discharge Criteria of Landfill Leachate’,‘The Criteria of Domestic Use in Groundwater Quality’, and ‘The Criteria of Domestic Use inSurfacewater Quality’ that promulgated by Korean Ministry of Environment.From the analysis results on the Salmi open-dumping landfill, C/N ratio was 18.9 andBOD/CODCr ratios in leachate were higher than 1/10. Based on the CLWS, this results seemedto imply that the process of leachate stabilization at this landfill was still proceeding.