 Chronic hepatitis B patients who have achieved HBsAg loss from interferon treatment will be enrolled and observed for 96 weeks. Serum HBV DNA, HBsAg, anti-HBs, HBeAg, and anti-HBe will be measured every 3 months during the observation period. Their liver function and chemistry tests are also performed every 3 months. The liver ultrasonic examination would be taken every 3-6 months. The primary measurement is the percentage of patients who have positive HBsAg andor a detectable level of HBV DNA. Following the completion of the study period, patients will be offered to participate in a long term study for further observation of additional 144 weeks. 