Introduction - The aim of this study is, on the one hand, to assess the knowledge and perception of risk regarding hepatitis B virus (HBV) infection among individuals seeking consultation at a free, anonymous screening clinic (CDAG) in Paris, and, on the other hand, to evaluate the acceptability of vaccination. Methods - Between April and May 2007, clients at the CDAG were asked to complete a questionnaire assessing their HBV risk factors (RFs), knowledge, perception of infection risk, and acceptance of vaccination. An association between the perception of being at risk for HBV infection and HRs and sociodemographic characteristics was examined using univariate and multivariate analyses. Results - Of the 511 questionnaires analyzed: 70% of respondents belonged to the HBV-at-risk population; 74% were aware of sexual transmission and 63% of blood-borne transmission; only 37% were aware of the possibility of chronic progression of the infection. Fifteen percent of respondents perceived themselves to be at risk for HBV. The risk factors significantly associated with this perception, in multivariate analysis, were having an HBV carrier in their social circle or as a partner (p=0.003), and being from an endemic area (p=0.02). Furthermore, 66% of those surveyed stated they would accept an offer of vaccination, and 21% of those who refused considered it dangerous. Among the patients screened, 55% were immune and 2% were HBsAg-positive. Conclusion - Given the high prevalence of hepatitis B risk factors among their patients, CDAGs could play a key role in hepatitis B prevention by providing information on the risk and offering vaccination. (R.A.)