The peanut (Arachis hypogea L.) seed oil was extracted from the seeds of the peanut that grows in SE Anatolia of Turkey. Oil was obtained in 50 wt/wt.%, by solvent extraction. Peanut (A. hypogea L) seed oil was investigated as an alternative feedstock for the production of a biodiesel fuel. Biodiesel was prepared from peanut by transesterification of the crude oil with methanol in the presence of NaOH as catalyst. A maximum oil to ester conversion was 89%. The viscosity of biodiesel oil is nearer to that of petroleum diesel and the calorific value is about 6% less than that of diesel. Peanut seed oil have about 8.3% less heating value than that of diesel oil due to the oxygen content in their molecules. The quality of biodiesel is most important for engine part of view and various standards have been specified to check the quality. The important properties of peanut oil and its methyl ester (biodiesel) such as density, kinematic viscosity, flash point, iodine number, neutralization number, pour point, cloud point, cetane number are found out and compared to those of no, 2 petroleum diesel, ASTM and EN biodiesel standards. The comparison shows that the methyl ester has relatively closer fuel properties to diesel than that of raw peanut seed oil. (C) 2008 Elsevier Ltd. All rights reserved.