The aims of this study were to investigate serum hepatitis B virus (HBV) DNA levels at different clinical stages in patients with chronic HBV infection, and to determine the serum HBV DNA level that discriminated HBeAg-negative chronic hepatitis B(CHB) cases from inactive HBsAg carriers. In all, 222 patients, encompassing 68 HBeAg-positive CHB patients (HBeAg-positive, ALT-elevation), 89 HBeAg-negative CHB patients (HBeAg-negative, ALT-elevation), and 65 inactive HBsAg carriers (HBeAg-negative, ALT-normal), were tested. The ALT levels had been tested more than twice during the previous six months, and the serum HBV DNA levels were quantified by a polymerase chain reaction-based assay. The serum HBV DNA levels of the HBeAg-negative patients were significantly lower than those of the HBeAg-positive patients (median 2.7 x 10⁴ vs. 1.6 x 10⁸ copies/mL; p=0.000). In addition, the HBV DNA levels of the HBeAg-negative CHB patients were significantly higher than those of the inactive HBsAg carriers (median 2.2 x 10⁵ vs. 3.2 x 10³ copies/ mL; p=0.000). The optimal HBV DNA level for discriminating HBeAg-negative CHB cases from inactive HBsAg carriers was 2.0 x 10⁴ copies/mL. The serum HBV DNA levels were lower than the cutoff value in 72.3% (47/65) of the inactive HBsAg carriers, and in 31.5% (28/89) of the HBeAg-negative CHB patients. The serum HBV DNA levels differed significantly between these two groups. However, the levels in the two groups overlapped extensively, preventing the definition of a differentiation cut-off value.