a b s t r a c tSeveral works in the literature indicate that the combination of physical-chemical treatment (coagulation/flocculation) and membrane separation process can be a promising alternative for landfill leachate treatment. The objective of the present work was to evaluate the fouling potential in membranes after pretreatment of raw leachate by coagulation/flocculation process. Samples of stabilized leachate from Gericinó controlled landfill (Rio de Janeiro City, Brazil) were used. FeCl 3 and Al 2 (SO 4 ) 3 were applied as coagulating agents. The pH and coagulant dosage were evaluated. Modified fouling index (MFI) and silt density index (SDI) were used to estimate the formation of deposits in the nanofiltration (NF) or reverse osmosis (RO) membranes for leachate treatment. SDI was not significantly reduced despite the great removal of suspended matter by the pretreatment. The MFI of leachate pretreated with FeCl 3 was 100 times lower than the MFI of leachate pretreated with Al 2 (SO 4 ) 3 and about 10,000 times lower than the raw leachate. This can be attributed to the influence that the organic matter exerts on the MFI. Therefore, the results showed coagulation/flocculation would be a good pretreatment for NF or RO treatment of landfill leachate.