This article analyzes the evolution of the debate on socio‐economic vulnerability, both in the United States and France, as well as commenting on the contemporary situation in Brazil. In the US study, which draws on the concept of ‘underclass’, the debate is openly political‐ideological — blaming the victims (or not) for their marginalization and anomie — which has made some authors regard the so‐called ‘well‐being programs’ as responsible for promoting a culture of dependency and family breakdown. In the French study, by contrast and following the republican tradition, both the diagnoses and proposals emphasize the need for a strong state presence to provide a means of reinserting  the  marginalized  groups.  The  article  doesn’t  attempt  a  critical  evaluation of the literature, but making use of seminal works it aims to show that the parameters of the theoretical and empirical problem depend on the particularities of each national political ambience. The final section on Brazilian society focuses on the marginality‐dependency debate of the 1970s and on what can be termed a process of disenfranchisement that affects the urban poor. Final comments are made concerning the matrix of extreme inequalities characterizing Brazilian society vis‐à‐vis the French and American cases.