In this study, leachate samples from the IZAYDAS landfill were collected and analyzed for a period of 30 months from December 2001 to May 2004. The landfill is located in the city of Kocaeli in Turkey and it has been in use since 1998. The leachate is pre-treated by a full-scale physico-chemical treatment system prior to transportation to the municipal wastewater treatment plant for a final treatment and disposal. Chemical analyses were performed on both raw and pre-treated leachate samples and the temporal variation of several parameters were monitored including pH, COD, SS, phenol, Total P, S-2, CN-, Ba, and selected heavy metals (Cr, Ni, Cu, Zn, Cd, Hg, As, Sn, Sb, Pb). The data collected were fitted with trendlines to represent temporal variations. Principal component analysis (PCA) as a multivariate statistical method was later used for filtering the data so that only the significant independent variables could be determined. While the method identified Cu, Total P, Zn, and COD for the raw leachate, Zn, Cu, Total P, S, and COD were the ones most essential for explaining the variation within the data for the pre-treated leachate. The concentrations of the most of the parameters in the raw leachate were lower than the ranges reported in the literature. The results show that a physico-chemical treatment planting incorporating a dissolved air flotation (DAF) stage can be used as an effective alternative for landfill leachate pre-treatment.