Patients with chronic hepatitis B virus (HBV) infection are at risk for development of liver cirrhosis and hepatocellular carcinoma. The goal of antiviral therapy for chronic hepatitis B is the permanent suppression of HBV replication; loss of HBV DNA and HBeAg seroconversion. Three antiviral drugs-interferon, lamivudine and adefovir dipivoxil-are avilable now. Although they were proven to have suppressive effects on HBV replication, their antiviral effects are not satisfactory yet and durability of response is low. Emergence of drug resistant mutants is troublesome in lamivudinr therapy. Expense of drugs is another problem for long-term antiviral treatment. Development of new drugs which have stronger and durable antiviral effects and combination therapy with several antiviral drugs to reduce drug resistant mutants are anticipated.