Latin America has been a world pioneer of neoliberal, structural reform of social security pensions (‘privatisation’). This article focuses on the diverse political economy circumstances that enabled such reform, analysing why policy makers have chosen such a costly strategy and how they have managed to implement it. First, in nine countries with diverse regimes (authoritarian and democratic) it examines the internal political process that led to the adoption of reform. There tends to be an inverse relationship between the degree of democratisation and that of privatisation, but the political regime alone cannot fully explain the reform outcomes in all cases. To expand the search for explanatory variables, other key factors that might have influenced the reform design are studied, among them relevant political actors (driving and opposing forces), existing institutional arrangements, legal constraints, internal and external economics and policy legacy.