This paper is an analysis of the study by Yotsuyanagi et al. about the association of hepatitis B and other viruses in the etiology of non-B and non-C hepatocellular carcinomas. The authors tested for hepatitis B, hepatitis C and transfusion transmitted virus in patients suffering from hepatocellular carcinomas in Japan. Although many of these patients were negative in respect to anti- HBs and / or anti- HBc, using PCR it was possible to prove many individuals exhibited DNA of hepatitis B virus in the blood serum. The most significantly findings were in patients negative for both anti- HBs and anti- HBc. Using RT-PCR the presence of RNA of hepatitis B virus was found in the hepatic tissue in all cases, whether neoplastic or not, except in one patient.