BACKGROUND/AIMS: Lamivudine is highly effective in suppressing hepatitis B virus replication and hepatitis B induced necroinflammatory activity. The objective of this study was to evaluate the virological and biochemical responses to lamivudine by patients with HBV associated chronic liver disease. In particular we stressed the importance of lamivudine therapy by patients with decompensated liver cirrhosis. METHODS: We conducted a one-year trial of lamivudine in 80 patients with HBV associated chronic liver disease (chronic hepatitis 44, cirrhosis 36). We classified these patients according to the severity of hepatic dysfunction as chronic B hepatitis (Group A) or liver cirrhosis (Group B). These patients were treated for 12 months with 100 mg daily doses of lamivudine. RESULTS: The seroconversion rate of HBeAg was 23.5% in group A patients and 26.7% in group B patients. The negative conversion of HBV-DNA was sustained for one year in 79.5% of patients in group A and 86.1% in group B. The normalization rates of serum ALT were 90.9% in group A and 88.9% in group B patients. No serious side effect after discontinuance of the treatment was found. There were 12 ALT breakthrough cases and all of them showed mutation of YMDD motif. However, they did not deteriorate clinically in spite of ALT elevation and HBV-DNA reappearance. The Child-Pugh scores improved even in patients with decompensated liver cirrhosis. CONCLUSION: One-year lamivudine treatment resulted in excellent virological and biochemical improvements and was well tolerated in the patients with HBV associated chronic liver disease, even in decompensated cirrhosis. We conclude that lamivudine is relatively safe in chronic hepatitis B and liver cirrhosis treatment.