Chronic hepatitis B (CHB) is a serious disease in Taiwan, leading to substantial morbidity and mortality including hepatic failure, liver cirrhosis, and hepatocellular carcinoma (HCC). Recently a large body of evidence supports that high level of serum HBV DNA is an independent risk factor for late complications in CHB patients. Nucleos(t)ide analogues (NUC) are effective antiviral therapy that can potently inhibit replication of hepatitis B virus (HBV), and has been widely used in management of patients with CHB. Current practice guidelines recommend using serum alanine aminotransferase (ALT) > 2 times of the upper limit of normal (ULN) as the prerequisite to initiate antiviral therapy in compensated CHB patients without liver cirrhosis. However, serum ALT level does not exactly correlate with serum HBV DNA or liver tissue injury. Whether antiviral therapy improves outcomes of patients with slightly elevated ALT (i.e. 1-2 folds of ULN) remains unknown.