In this study, the significance of hepatitis virus (HBV) X gene mutations for the pathogenesis of HBV-associated glomerulonephritis (HBV-GN) was investigated. DNA was extracted from 50 HBV-GN patients and 60 asymptomatic HBV carriers and subjected to PCR amplification and sequencing of HBV X gene. In HBV-GN patients, missense nucleotide mutations of C1653T, A1726C, A1727T, C1730G, T1753C, A1762T, and G1764A were detected in 84% of subjects, all located in the trans-acting regulatory region of the X gene. In control patients, missense nucleotide mutations of A1632C and A1635C were detected in 8% of subjects, both located in the non-functional region of the X gene. We conclude that, in most HBV-GN patients, X gene missense mutations occurred at some key sites playing an important role in the pathogenesis of HBV-GN.