Abstract： Objective To investigate the efficacy and safety of adefovir dipivoxil(ADV)for chronic hepatitis B(CHB)patients with lamivudine(LMD)resistance.MethodsA total of 247 LMDresistant CHB patients were included in this multi-center,randomized(1:1),double-blinded and LMDcontrolled clinical trial.All subjects were swithed to open-labelled ADV treatment after 12-week doubleblinded stage.Serum HBV DNA and ALT levels were monitored and safety assessments were conducted at 12th and 48th week during the treatment.Results At 12th week.mean reduction of ALT in trial group was 35.9 U/L,and the reduction of HBV DNA was 3.01 log10 copies/mL.The reductions of HBV DNA in 61.8%(76/123)subjects were more than 2 log10 copies/mL.While in the control group,ALT raised 2.8 U/L in average,and the reduction of HBV DNA was 0.78 log10 copies/mL.The reductions of HBV DNA in 17.7%(22/124)subjects were more than 2 log10 copies/mL.At 48th week,mean reduction of ALT in trial group was 59.7 U/L,and the reduction of HBV DNA was 4.70 log10 copies/mL.The reductions of HBV DNA in 87.0%(107/123)subjects were more than 2 log10 copies/mL.While in the control group,mean reduclion of ALT was 56.6 U/L,and the reduction of HBV DNA was 4.43 log10 eopies/mL.The reductions of HBV DNA in 85.5%(106/124)subjects were more than 2 log10 copies/mL.No severe adverse effect related to the investigational product was observed in both groups.Conclusion ADV is safe and effective in the treatment of LMD-resistant CHB patients with virological and biochemical improvements.