A micro-state located on the frontier between Spain and France in the middle of the Pyrenees, Andorra was a very poor country traditionally based on pastoralism. It has become nowadays a free trading zone involved in commercial and financial international flows. In this article, we analyse the structural and strategic role of the frontier as it defines the economic system of the country and the lifeways of its inhabitants. We also discuss the various forms of endogenous frontiers (social, legal and cultural) which divide people and make of Andorra a society organised through significant internal segmentation. The country also hosts a large proportion of foreign workers next to a national and hegemonic minority based on the control of political power and the preservation of old privileges.