This article first discusses the modes of the social construction of memory in certain favellas (shanty towns) of Rio de Janeiro in Brazil. It argues that forms of denial of social history constitute a defensive process by which the pain of social origin is silenced or chased away. This article also discusses the kinds of projects a social group can have by examining the types of imaginary which animate them. Secondly, this article studies one particular favella in Rio de Janeiro. On the basis of an action-research project conducted with the collaboration of its inhabitants, the author explains the project and the stages of the group's intellectual and affective construction. Such a rediscovery of collective history is essential to a community's development.