In 2009, the French Institute for Public Health Surveillance launched the first HIV seroprevalence survey among men who have sex with men (MSM) frequenting gay social venues in Paris. The anonymous cross-sectional survey was conducted in Paris at 14 commercial gay social venues (saunas, backrooms, and bars). MSM provided a blood sample via self-collection of capillary blood from their fingertips onto a blotter paper, then completed a self-administered behavioral questionnaire. Testing for HIV antibodies was performed in the laboratory using the Genscreen ultra HIV AgAb® test (Biorad); positive samples were confirmed by Western blot. A total of 919 MSM agreed to participate (58%). The prevalence of HIV was 17.7% (95% CI [15.3–20.4]). HIV testing in the past 12 months was reported by 62%. However, 20% of HIV-positive MSM were unaware of their HIV status. Sexual activity and risky sexual behaviors were common among HIV-positive MSM. Although the results cannot be generalized to the entire MSM population, they support continuing preventive measures in gay social venues while promoting appropriate screening. (R.A.)