The research activities from past two decades have been vigorously done in the area of alternate fuel for CI engine and still it is on. The rapid industrialization and motorization airs is a serious threat to the draining of petroleum resources. Many investigations and studies revealed that the oils from the vegetable origin can be successfully implemented to the existing CI engines without any major hardware modification and still further research is necessary to find a fuel resource from a waste recovery point of view. In this regard, waste cooking oil/frying can be used as a potential alternative fuel. This paper reviews the production, potential, characterization, engine performance and exhaust emissions of the waste cooking oil biodiesel through the experimental work carried out in various part of the world.