In the 1990s, the fight against HIV became a national cause, the preventive initiatives of which addressed the entire population to avoid any stigmatization. In the 2000s, recognizing the existence of “high-risk groups” no longer posed a problem and determined more targeted action. In response to the resurgence in risk-taking, the players involved in these efforts worked to understand groups through the close observation of their behaviour. Focusing on male homosexuals, the article analyses two recent innovations embodying this trend: the demedicalization of screening and pre-exposure prophylaxis. These developments show that the observed changes are not simply about expressing what should not be said, but instead involve renewed work on objectivation, the mobilization of members of the target population, and a certain idea of the risk-taking individual. The detection of at-risk behaviour also serves to delimit the populations with which intervention is possible and the implementation of the necessary tools.