Current guidelines for management of chronic hepatitis B recommend treatment for patients presenting with elevated hepatitis B virus (HBV) DNA and alanine aminotransferase (ALT) >2 × upper limit of normal (ULN) or histological evidence of liver disease. Retrospective analyses have demonstrated that significant hepatic necroinflammation and fibrosis were present in a substantial proportion of patients with ALT 1 to 2 × ULN. To assess therapeutic efficacy in this clinical setting, we retrospectively examined treatment endpoints among the subset of nucleoside-naïve chronic hepatitis B (CHB) patients treated in phase 3 clinical trials of entecavir who had both screening and baseline serum ALT 1.3 to 2 × ULN. A total of 1347 patients were randomized to treatment with entecavir or lamivudine. Three hundred thirty-six patients, constituting 25% of the total study population, had screening and baseline ALT 1.3 to 2 × ULN. Clinically significant necroinflammation (Knodell necroinflammation score ≥7) was observed in 60% and 72% of hepatitis B e antigen (HBeAg)-positive and HBeAg-negative patients, respectively, whereas marked fibrosis (Ishak fibrosis score ≥4) was observed in 8% and 15% of HBeAg-positive and HBeAg-negative patients, respectively. Among entecavir-treated HBeAg-negative patients, the proportions of patients achieving histological improvement, HBV DNA <300 copies/mL, and ALT normalization were similar between patients with mildly elevated ALT and those with ALT >2 × ULN. However, entecavir-treated HBeAg-positive patients with mildly elevated ALT had lower response rates for histological improvement, HBV DNA less than 300 copies/mL, ALT normalization, and HBeAg seroconversion than those with ALT greater than 2 × ULN. Conclusion: This retrospective analysis demonstrated that HBeAg-negative CHB patients treated with entecavir responded similarly irrespective of baseline ALT level. However, HBeAg-positive patients with mildly elevated ALT responded less well to treatment with entecavir than did those with ALT greater than 2 × ULN. (HEPATOLOGY 2010.)