Viral hepatitis is the most common cause of acute and chronic hepatitis. The term, viral hepatitis, generally refers to infections resulting from one of the hepatotrophic viruses: hepatitis A, B, C, D and E. As hepatitis B virus (HBV) and hepatitis C virus (HCV) mainly cause chronic hepatitis and hepatocellular carcinoma, early diagnosis, prevention and viral elimination are necessary. Eight genotypes of HBV have been detected by sequence divergence of >8% in the entire HBV genome, and designated by capital letters from A to H in the order of documentation. They have distinct geographical distribution and influence the severity of liver disease as well as the response to antiviral therapies. Similarly, HCV has at least six genotypes, of which HCV-1 and -2 are the major genotypes worldwide. Only interferon therapy can eradicate HCV at present, and the sustained virological response depends on HCV genotypes and viral loads. Here, we summarize examinations based on viral nucleic acids and the clinical manifestations of HBV and HCV genotypes.