Biodiesel is an emerging alternative to diesel fuel, which has received much attention with respect to environmental concerns and fuel security of the world. Vegetable oils and animal fats are the major feedstock for biodiesel production. The quality of the feedstock is the vital criterion in selection of a suitable biodiesel production technology. The purication of the end products and production plant economics play an important role in the commercial evaluation of biodiesel. The various biodiesel production technologies, that is, alkaline, acid, two-step, ultrasonic, lipase, and supercritical alcohol are discussed in this chapter. Process parameters such as molar ratio of the alcohol to oil, the catalyst amount, reaction temperature, and water content with respect to the yield are also analysed. The comparison of various biodiesel production technologies, properties of biodiesel and their testing methods, the inuence of chemical composition of biodiesel on storage, and its use in engines are discussed.