Over the past few years, cultural dynamics has again become a central concern. The approach to the problem is predominantly theoretical. The author considers that it is more fruitful to examine it on the basis of real cases. From this perspective he gives a “biography” of Halloween, a celebration based both on an original account that affirms its millenary existence, and a recent story made of successive transformations. He studies its evolution from its appearance in modern times in the Anglo-Irish islands to its implantation in the United States and Canada in the late nineteenth century and to its present-day vicissitudes. His analysis points out that one of the conditions for the perpetuation of this celebration is precisely the great flexibility of the uses connected to it.