OBJECTIVE To study the clinical significance of hepatitis B surface antigen (HBsAg) levels and HBsAg/hepatitis B virus (HBV) DNA ratio in relation to liver inflammation in HBeAg-positive chronic hepatitis B (CHB). METHODS One hundred and fifty-three Chinese patients with chronic HBV infection with HBeAg-positive status were enrolled in the study.Quantitative measurements were made for HBsAg levels by immunoassay (Architect HBsAg QT by Abbott Diagnostic) and HBV DNA by real-time fluorescence quantitative PCR.Levels of liver function markers were measured by standard methods.Liver biopsy specimens were obtained from all patients and used to score the histology (liver inflammation) activity index (HAI) and grade (G) the extent of necroinflammation.Statistical correlation analysis was performed to determine the association of HBsAg titre or HBsAg/HBV DNA ratio with the various parameters of liver injury. RESULTS HBsAg titre and HBsAg/HBV DNA ratio were significantly correlated (r =0.578, P less than 0.0001).A significant positive correlation (r =0.642, P less than 0.0001) was found between HBsAg titre and HBV DNA load, and a significant negative correlation was found between the HAI and HBsAg (r =-0.389, P less than 0.0001) and HBsAg/HBV DNA ratio (r =-0.307, P=0.000l).A significant positive correlation was found between alanine aminotransferase (ALT) level and the HAI (r =0.480, P less than 0.0001).Patients with G less than 2 necroinflammation had significantly higher HBsAg titre and HBsAg/HBV DNA ratio than patients with G more than or equal to 2 necroinflammation (both P less than 0.01) but similar levels ofHBV DNA.Generation of a receiver operating characteristic curve using G more than or equal to 2 as the positive index provided the following area under the curve (AUC) values:HBsAg titre, 0.700; HBsAg/HBV DNA ratio, 0.672; ALT level, 0.713.When the random chance AUC was 0.5, all levels of AUC were statistically significant (Pless than 0.001).HBsAg titre (sensitivity =76.92%) was more sensitive than ALT level (sensitivity =76.92%), and HBsAg/HBV DNA ratio (specificity =81.33%) was more specific than ALT level (specificity =81.33%).Youden's index for comprehensive evaluation using ALT was higher than those for HBsAg titre or HBsAg/HBV DNA ratio.When HBsAg and ALT were considered in parallel, the sensitivity increased to 94.08% and specificity rose to 85.60%. CONCLUSIONS HBsAg titre, HBsAg/HBV DNA ratio and ALT levels can be used as the index for judging the degree of liver inflammation in HBeAg-positive CHB patients.Higher sensitivity and specificity are attained when HBsAg and ALT are used in series or parallel.