Lamivudine therapy improves hepatic necro-inflammatory activity, decreases progression of fibrosis, and suppresses hepatitis B virus (HBV) replication. Famciclovir has also been shown to have some effect in the suppression of HBV replication. The aim of the study was to compare the effect of treatment with lamivudine and famciclovir on serum HBV DNA levels in patients with chronic hepatitis B and to assess safety. A prospective randomised clinical study was carried out on 100 patients with chronic hepatitis B infection (50 patients received lamivudine 100 mg daily and 50 patients received famciclovir 500 mg three times a day for 12 weeks. From the twelfth week onwards, patients were offered lamivudine 100 mg daily up to 48 weeks). Significantly more patients treated by lamivudine than by famciclovir had undetectable HBV DNA levels after 12 weeks of therapy (P < 0.001). The median HBV DNA levels were significantly lower in the lamivudine-treated patients from the second week of treatment onwards (P < 0.001 for all time points up to 12 weeks). At week 16, 4 weeks after the famciclovir treated patients were put on lamivudine, there was no longer any difference in HBV DNA levels between the two groups of patients. Both treatments were well tolerated and no serious adverse events were reported. It was concluded that in Chinese patients with chronic hepatitis B infection, lamivudine achieved effective suppression of HBV DNA levels within 4 weeks of therapy whereas famciclovir had a significantly weaker action. J. Med Virol. 67:334–338, 2002. © 2002 Wiley-Liss, Inc.