In this paper we discuss how the practices and the scope of political action can be a mode of subjectivation for young people today. By means of the analysis of 19 interviews with Brazilian youngsters of Rio de Janeiro, where their militancy in schools, colleges, and political parties was investigated, we could determine three central aspects which qualify the process of self construction through political activism: the facing of unknown outcomes, the relevance of action in the present, and the conflicts between public and private spheres, which demand totalizing the field of identifications. [ABSTRACT FROM AUTHOR]