A recombinant immunoscreening approach was used to clone and identified the genome of the non-A, non-B hepatitis virus. This agent is a positive-stranded RNA virus that appears to be distantly related to the flaviviridae family. A recombinant viral antigen (C100-3) was used to develop a "capture" assay for circulating antibody. Data obtained using this assay indicate that this agent, termed the Hepatitis C virus (HCV), is the major cause of post-transfusion, community-acquired and cryptogenic, NANB. HCV is associated with the development of hepatocellular carcinoma and possibly, other liver diseases. In this article the characteristic of Hepatitis C virus were discussed.