The major studies on men who have sex with men (MSM) in France (which began with Michael Pollak and Marie-Ange Schiltz forty years ago in Gay Press) introduced the idea of drug use in 1997, just after highly effective antiretroviral treatment (HAART) combinations were made available for HIV, making AIDS a manageable chronic condition. Australian researcher Kane Race identifies this time as the beginning of a “lifetime of drugs”, but the utility of surveys into the use of psychoactive substances among gay people was to emerge in the following decades, after it was discovered that ARV treatments could keep viral load at undetectable levels in HIV-positive people, who could therefore no longer infect others. In the early 2010s, the use of drugs became a major theme in surveys of gay sexuality, and in particular the use of drugs in a sexual setting, which was named “chemsex”. Men who adopt this practice tend to have intense sex lives, with a very large number of sexual partners over the past 12 months, regular attendance at sexual meeting places, specific sexual practices and do not use condoms for anal penetration. The majority who are involved are HIV-positive MSM or HIV-negative MSM on PrEP. To date, the research and publications looking at chemsex have only investigated it through the prism of the associated risks linked to addiction and compulsive behaviour. In this article we intend to show how the emergence of a scientific literature of chemsex has contributed to a masking of the strictly sexual behaviours associated with it. We will draw upon two complementary types of material: several quantitative surveys of sexual and HIV prevention behaviours among gay men and other MSM (Prevagay 2015, the 2017 “Rapport au Sexe” survey, known as ERAS). and the initial results of the APACHES survey (Attentes et PArcours liés au CHEmSex/Expectations and Experiences of Chemsex), which used biographical interviews carried out on behalf of OFDT in 2018, focusing on sexual scripts as well as the role of pleasure and contemporary ways of socialising in this subculture.