Hepatitis B and C viruses produce chronic infections of the liver which may lead to long term disease and cancer. It has been estimated that 1-5% of the US population is now infected with hepatitis C virus (HCV), and hepatitis B virus (HBV) infection is also common. Worldwide, infection by these viruses are the major cause of heptocellular carcinoma. The overall goals of our research are to characterize how these viruses replicate, their interactions with the infected host, the steps which lead to cell transformation and tumor outgrowth, and the effects of antiviral therapy on the long-term consequences of infection.