Introduction. Since March 2003, surveillance of acute hepatitis B virus infections has been based on mandatory case reporting. Here we present the results of this surveillance from 2004 to 2006. Methods. Biologists and clinicians report cases of acute hepatitis B to the Departmental Directorate of Health and Social Affairs, defined as follows: any person in whom anti-HBc IgM antibodies are detected for the first time; failing that, any first detection of HBs antigen and total anti-HBc antibodies in the context of acute hepatitis. A national retrospective survey was conducted in 2006 to assess the completeness of the reporting system and estimate the incidence, by randomly selecting medical testing laboratories according to a stratified random sampling plan, and then examining the tests performed by these laboratories. Results. 469 cases meeting the reporting criteria were identified as acute hepatitis B, with a predominance among men and those aged 30–49. No risk exposures were identified in 28.9% of cases. The most frequently documented exposures were: risky sexual behavior (35.5%), travel to countries with moderate or high endemicity (22.6%), household exposure (8.3%), and living in an institution (5.3%). Drug use was identified in just over 2% of cases. Half of the reported cases could have been prevented if current vaccination recommendations had been followed. The completeness survey shows that the number of cases in 2005 can be estimated at 628 [95% CI: 564–694], representing an incidence of 1 case per 100,000 inhabitants [95% CI: 0.92–1.14]. Conclusion. It appears imperative in France to improve the implementation of vaccination recommendations and case-based prevention measures, with enhanced screening for at-risk individuals.