Whether resistant hepatitis B virus (HBV) strains are transmissible and can lead to chronic infection remains to be studied. The aim of this study was to investigate the clinical characteristics of patients with acute hepatitis B caused by lamivudine (LAM)-resistant strains. Sera were collected from 234 Chinese patients with acute hepatitis B. LAM-resistance mutations were identified by direct polymerase chain reaction (PCR) sequencing. LAM-resistant HBV variants were detected in 11 of the 234 (4.7%) patients. Among these patients, six harbored the rtM204I mutation, two harbored the rtL180M + rtM204I mutations, one harbored the rtM204I + rtM204V mutations, one harbored the rtL80I + rtM204I mutations, and one harbored the rtV173L + rtL180M + rtM204V mutations. Three patients were infected with genotype B HBV and eight patients were infected with genotype C HBV. Two patients infected with viruses with LAM-resistance mutations developed severe acute hepatitis. One patient developed chronic hepatitis B. This patient was infected with genotype C HBV that had LAM-resistance mutations (rtL180M + rtM204I). The patient was diagnosed with an occult hepatitis B virus infection based on the presence of HBV DNA in the liver and the absence of detectable hepatitis B surface antigen (HBsAg) in the serum. LAM-resistant HBV strains in China are transmissible, can cause acute hepatitis B, and can even progress to chronic infection in China. J. Med. Virol. 84:1558–1561, 2012. © 2012 Wiley Periodicals, Inc.