In this study, animal fat obtained from leather industry fleshing wastes was used to produce methyl ester. The acid value of the fleshing oil was 24.30 mg KOH g (1) which corresponds to FFA level of about 12.15%. Therefore, it was needed to perform a pretreatment to the fleshing oil. For this aim, sulfuric acid was used as a catalyst and methanol was used as alcohol for pretreatment reactions. The variables affecting the FFA level including alcohol molar ratio and catalyst amount were investigated by using the fleshing oil. After reducing the FFA level of the fleshing oil to less than 1%, the transesterification reaction was completed with alkaline catalyst. Potassium hydroxide, sodium hydroxide, potassium methoxide and sodium methoxide were used as catalyst and methanol was used as alcohol for transesterification reactions. The effects of catalyst type, catalyst amount and alcohol molar ratio on the fuel properties of produced methyl esters were investigated. The measured fuel properties of the fleshing oil methyl ester (FOME) were compared to EN 14214 and ASTM D6751 biodiesel standards. According to results, the cold flow properties of FOME should be improved and the sulfur content of FOME should be investigated in detail. (C) 2011 Elsevier Ltd. All rights reserved.