Carbon-carbon single bond-forming reaction is the most useful and fundamental reaction in organic synthesis. Most of the basic carbon-carbon single bond-forming reactions, thus, developed in the past. In these respects, conceptually new C-C bond formation reaction can be highlighted. The Baylis-Hillman reaction was found at the early 1970’s. However, extensive studies on this highly potential reaction were started only before 15 years. This review has been written to shed more lights to the importance of Baylis-Hillman reaction. We have focused mainly on the reaction mechanism, conceptually related reactions, and chemical transformations of the Baylis-Hillman adducts.