The NANJIDO, an unregulated landfill site was closed about 14 years before. After complete installation of final cover systems like physical training, a public garden and artificial ponds, this was well harmonized with surrounding facilities. Hence, the present study was focused on evaluating the stability of the landfill, by analyzing the data of landfill gas and leachate obtained from 2003 to 2007. The average CH4 concentration in 2007 has been decreased to 5 ~ 8%, when compared with the average concentration of CH4 in 2003. However, the presence of high concentration of CH4 (40%) indicates the stabilization process is not yet completed. The rate of leachate generation was found to be increasing in July and reaches the maximum during August and September. Interestingly, the total rate of leachate generation has been decreased from 2004. The BOD concentration was below than 20 mg/L. In general, the concentraion of BOD, CODCr, and NH3-N in landfill No. 1 was relatively higher than landfill No. 2.