Recently, two groups reported independently on the isolation of new positive-trand RNA viruses, designated hepatitis G virus (HGV) & GB virus C (GBV-C). Sequence analysis revealed that both genomes are different isolates of the same virus & represent a new genus of Flaviviridae. The prevalence of HGV ranges from 0.9 to 10% among blood donors throughout the world. A high prevalence of HGV RNA has been found in subjects with frequent parenteral exposure, including intravenous drug users, patients on hemodialysis, patients with hemophilia and patients with anemia. HGV is a blood borne virus that is parenterally transmitted. Vertical transmission has also been reported. HGV commonly occurs as a coinfection with another hepatitis virus such as HCV or HBV. However, HGV coinfection usually does not alter the clinical course or level of biochemical marker and the response to antiviral therapy of chronic hepatitis B or C in these patients. Acute HGV infection rarely causes acute hepatitis and is unlikely to be a major cause of chronic non-A-E hepatitis or fulminant viral hepatitis. HGV infection can be diagnosed by PCR assay to detect the viral RNA in serum. An enzyme-linked immunosorbent assay (ELISA) for detection of antibodies to recombinant HGV putative envelope protein E2 was recently available. But antibodies to E2 appears to be a serological marker for diagnosing recovery from HGV infection. Since the role of HGV as a etiologic agent of liver disease is unclear, therapy is not recommended at this point.