Background: Chronic hepatitis B virus (HBV) infection is a serious global public health problem associated with cirrhosis, liver failure and hepatocellular carcinoma. Tenofovir disoproxil fumarate and adefovir were licenced for the treatment of hepatitis B virus infection. Aims: The aim of this study was to evaluate the efficacy and safety of tenofovir, as compared with adefovir in patients with chronic hepatitis B. Patients and Methods: The study enrolled 61 chronic hepatitis B patients with compensated liver disease. The tenofovir group consisted of 31 patients who received tenofovir 300mg/day and adefovir group consisted of 30 patients who received adefovir 10mg/day. Patients returned to hospital every four weeks for laboratory assessment of serum chemical and hematologic values, liver fimction and for documentation of any adverse events. Hepatitis B serologic markers and HBV-DNA levels were assessed every 12 weeks. The primary efficacy end-point was a plasma HBV-DNA level of less than 69 copies/ml over 48 weeks. Results: At the end of 48 weeks, 27 tenofovir-treated patients (87,1 percent) and 14 adefovir-treated patients (46,7 percent) achieved HBV-DNA69 copies/ml (p