Among the options explored for alternative energy sources, bio-diesel is one of the most attractive. This paper discussed about the various production processes, few of which are applied at industrial level also, to produce basically FAME (later can be utilized as bio-diesel after purification) and will be termed as bio-diesel in this paper. Transesterification of vegetable oils/fats and extraction from algae are the leading process options for bio-diesel production on large scale. This paper reviews briefly the literature on transesterification reaction using homogeneous, heterogeneous and enzyme catalysts. Employing also ultrasound, microwave and supercritical alcohol techniques and also algae based bio-diesel. (C) 2009 Elsevier Ltd. All rights reserved.