In September 2008, an acute hepatitis B virus (HBV) infection was reported to the Gard Departmental Directorate of Health and Social Affairs in a teenage girl whose only risk factor was acupuncture sessions at a Chinese energy therapy center. An inspection of the center confirmed the illegal practice of medicine and a failure to comply with standard hygiene precautions. In addition to the failure to comply with standard precautions, the inspection noted the presence of soiled needles or cupping cups that had potentially been reused. A prefectural order mandated the cessation of operations, and an investigation was initiated to actively identify other cases (through mandatory reporting, public information via the press, and letters to physicians), describe their clinical, biological, and epidemiological characteristics, and characterize and compare the strains via sequencing at the National Hepatitis Reference Center. A case was defined as an acute HBV infection (presence of HBs antigen and anti-HBc IgM) occurring in any client who had visited the center in the preceding 6 months. In total, 4 cases (including 1 asymptomatic case) were identified among female clients aged 16 to 85; none had been vaccinated and none reported other risk factors. Two had received treatments on the same day, but no chain of transmission could be identified. All four strains were genotype D and showed 100% sequence homology in the analyzed regions (for three strains, the entire viral genomes were compared; the fourth strain was analyzed across two independent genomic regions: the S and C genes). Furthermore, all four strains exhibited a mutation in the S gene (T131I). This is the first such episode described in France, and these results confirmed patient-to-patient HBV transmission likely linked to the use of contaminated and/or shared equipment. Acupuncture in France is a medical procedure that must strictly adhere to standard precautions. (R.A.)