Abstract : From a sociological perspective, this PhD dissertation analyzes how the norms of Aids prevention have been transformed among gay men in France. The research rests on a qualitative investigation which delves into study the controversies between associations about HIV risks (1989- 2009) and the analysis of lay experience of prevention among gay men. On diverse social scales, it aims at highlighting how agreements and disagreements about prevention show different conceptions of the relationships between homosexuals. Studying the emergence of the phenomenon of bareback in the French media, this dissertation proposes a sociohistorical reading of the way risks have been problematized, related to a sociological analysis of the elaboration and circulation of prevention standards. The underlying reflexive anthropology shed light on the situated rationalities of risk management in Aids era.