This study aimed to investigate sex differences in relation to hepatitis B e antigen (HBeAg) and serum alanine aminotransferase (ALT) levels in chronic asymptomatic hepatitis B virus (HBV) infection. HBeAg and ALT level were determined in 636 asymptomatic hepatitis B surface antigen carriers. There was no significant sex differences in the age-adjusted prevalence of HBeAg. Abnormal ALT level (>45 IU/l) was more frequent in carriers with HBeAg (17.5% vs 7.6%; P = 0.001). Multivariate analysis indicated that male sex (odds ratio, 2.0; 95% confidence interval, 1.1-3.6) and HBeAg (odds ratio, 2.6; 95% confidence interval, 1.6-4.3) were independent risk factors for abnormal ALT levels. Male sex and HBeAg-positivity are independent risk factors for abnormal ALT activity in chronic HBV infection. This observation may be related to sex differences in chronic HBV infection.