Background: Entecavir has been shown to be effective in randomized controlled trials in highly selected patients with hepatitis B virus infection. Entecavir does not cure HBV and may not prevent complications of hepatitis B such as cirrhosis of the liver or liver cancer. The dose is double for people who have persistent hepatitis viremia (the presence of virus in the blood) while taking lamivudine or have lamivudine reesistance. It’s recommended to take entecavir on an empty stomach, two hours before or after a meal. For some people, hepatitis B infection become chronic, meaning it lasts more than six months. Having chronic hepatitis B increases your risk of developing liver failour, liver cancer or cirrhosis a condition that permanently scares of the liver. Aims: This study aimed to evaluate the efficacy of in cronic hepatitis B patients in the real world setting. Methodology: In this study a total of 32 acute on chronic Hepatitis B liver failure patients (age > 18 years with both sexes but male predominant) were included in Hepatology department of Bangabandhu Sheikh Mujib Medical University, Dhaka during January 2013 to December 2015. The patients were randomized into two groups: Entecavir group (N=32) and followed at least for 03 months. Result: Table I shows the Majority 26(81.3%) patients were male and 6(18.7%) patients were female in entecavir group. Altered level of consciousness was found 14(43.8%) in entecavir group. Moderate ascites was found 26(81.3%) in entecavir group. Encephalopathy was found 16(50.0%) in entecavir group. The entecavir not statistically significant (p>0.05) of the groups. Table II shows Baseline investigation of the study patients (n=32). It was observed that mean total countwas found 10181.3±3594.1 /mm3 in entecavir group. Mean serum bilirubinwas found 22.0±5.7 mg/dl in entecavir group. Mean Rank ALT was found 18.0 U/L in entecavir group. Mean Rank AST was found 17.8 U/L in entecavir group. Mean prothrombin time was found 23.1±4.2 secant in entecavir group. Mean international normalized ratio was found 2.0±0.3 in entecavir group. Mean serum albumin was found 2.3±0.5 gm/dl in entecavir group. Mean serum creatinine was found and 0.85±0.31 mg/dl in entecavir group. Mean serum sodium was found 134.1±5.2 mmol/l in entecavir group. Mean serum potassium was found 3.7±1.0 mmol/l in entecavir group. Mean MELD scorewas found 26.5±2.0 in entecavir group. Mean Child Pugh scorewas found 12.0±1.5 in entecavir group. The mean entecavir was not statistically significant (p>0.05) of the groups. Liver function, Child Pugh score and MELD score improvement by three months after entecavir therapy: In entecavir patients, mean serum bilirubinwas found 22.0±5.7 mg/dl in pretreatment and 5.1±1.7 mg/dl at 90 days. Mean international normalized ratio was found 2.0±0.3 in pretreatment and 1.4±0.2 at 90 days. Mean serum albumin was found 2.3±0.5 gm/dl in pretreatment and 3.1±0.3 gm/dl at 90 days. Mean Child Pugh scorewas found 12.0±1.5 in pretreatment and 9.3±0.9 at 90 days. Mean MELD scorewas found 26.5±2.0 in pretreatment and 17.0±2.1 at 90 days. Negative Mean Ranks ALT was found 4.0 U/L and sum of Ranks 28.0 U/L. Positive mean rank and sum of rank 0.The difference were statistically significant (p<0.05) between two groups. Table VIII: Entecavir induced improvement of liver function, Child pugh score and MELD score three months after therapy (n=16). Conclusion: In conclusion entecavir is very potent anti-HBV drug with a high genetic barrier to resistance, highly effective in lamivudine-naïve CHB patients and most promising for their long term treatment but not very suitable for CHB patients harboring LAM resistant HBV mutants.