Hepatitis G virus (HGV), for which there is no specific treatment because the exact pathogenic role of the virus in humans is unknown. HGV was originally cloned from a surgeon, and the virus was named GB virus (i.e., GBV) because of the initials of the surgeon’s name. RNA for GBV-C has been detected in patients with acute non-hepatitis A to non-hepatitis E viral hepatitis, in patients with chronic hepatitis of presumed etiologic origin, in patients with cryptogenic cirrhosis, and in some patients with primary hepatocellular carcinoma; however, it is often difficult to discern a direct role for GBV-C in these cases because of the commonity of co-infection with HCV. Currently, there are no prospective studies that histologically confirm the progression from acute GBV-C infection to different stages of chronic liver disease, such as chronic hepatitis, cirrhosis, and primary hepatocellular carcinoma. In patients with chronic non-A to non-E hepatitis or in patients with cryptogenic cirrhosis, there is no evidence yet to prove that GBV-C is a cause rather than an unrelated factor for these diseases. Therefore, upon detection of HGV infection, prompt medical attention and treatment under medical supervision are recommended.