Results: The level of HBsAg and HBsAb was 254.4±68.3 S/N and 39.4±38.1 mIU, respectively. HBV DNA was detectable in 46 patients. Fifty-one mutations of S gene were detected in 38 patients, and the relating amino acid substitution was at the sites of 36, 39, 47, 63, 77, 89, 90, 115, 126, 129, 139 and 154. Eight (15.7%) out of 51 mutations were located at the "a" determinant region in 14 patients, while no mutation was found at the sites of 124, 137 and 147. However, the mutation did not affect HBV replication. HBV DNA was positive correlated with HBeAg. Conclusions: Change in HBsAg antigenicity due to S gene resulted in concurrent HBsAg and HBsAb. The existence of HBsAb did not affect HBV replication. The damage of liver failure in those patients was slight. Background: HBV infection is common in Bangladesh. We often encounter young patients incidentally detected with HBeAg negative chronic hepatitis B (CHB) in our clinical practice. However the characteristics of these patients is yet to be studied in this country. The aim of this study was to study the characteristics of young Bangladeshis incidentally detected with HBeAg negative CHB. Methods: We did percutaneous liver biopsies of 36 CHB patients aged between 8 to 20 years. They were all HBeAg negative with persistently normal or raised serum ALT values. We did pre-core mutation (PCM) study in 4 patients who were randomly selected. Results: 56% patients had significant necro-inflammation (HAI-NI >3), while significant fibrosis (HAI-F >2) was seen in 17.6%. Serum ALT (cut off 42 U/L) was raised in 38.2%, while high HBV DNA load (>10 5 copies/ml) was observed only in 26.5%. PCM was negative in all 4. Conclusion: Although CHB patients between 10-20 years of age are supposed to be in immune clearance phase, which is characterized by low HBV DNA and HBeAg positivity, the study shows that HBeAg negative CHB is an entity that can also be seen in this age group and a significant percentage of such patients may have considerable hepatic involvement. This challenges our current concept about immune clearance state of HBV infection, although much larger study is needed to draw any specific conclusion. Background: HBV infection is common in Bangladesh, but characteristics of young patients incidentally detected with chronic hepatitis B is yet to be studied in this country. Methods: We did percutaneous liver biopsies of 88 CHB patients aged between 8 to 20 years. Results: Significant necro-inflammation (HAI-NI >3) was seen in 79.6% patients with HBeAg positive and 56% patients with HBeAg negative CHB, while significant fibrosis (HAI-F >2) was seen in 20.3% and 17.6% patients in these two groups respectively. Serum ALT (cut off 42 U/L) was raised in 37% HBeAg positive and 38.2% HBeAg negative patients, while in these two groups 87% and 26.5% patients respectively had high HBV DNA load (>10 5 copies/ml). Conclusion: HBeAg negative CHB is an entity that can also be seen in young population. A significant percentage of both HBeAg positive and negative patients may have considerable hepatic involvement.