This article analyses the failure of the Proyecto Marginalidad (Marginality Project), which the Ford Foundation financed in the 1960s, and the political and academic conflicts that it provoked. It takes into consideration the viewpoints of the principal actors involved (the director of the project, the Ford Foundation, and its critics). The original aim of the Marginality Project was to study the conditions of marginality of urban and rural populations in various Latin American countries, but it generated few results. The article shows that this outcome resulted from a series of ‘structural misunderstandings’, due to the fact that the different actors did not share what, in the words of Marc Angenot, might be called ‘social discourse’. In other words, their assumptions about what was thinkable and sayable in the Latin American context in the late 1960s and early 1970s diverged significantly, giving rise to a series of conflicts about the objectives and conduct of the project.