In order to investigate the role of hepatitis B virus (HBV) DNA in the pathogenesis of renal lesion in HBV-associated membranous nephropathy (HBVMN) patients, serial studies using an in situ hybridization technique at different time points were performed. Within 6 months after the onset of the disease, 7 of 8 (87.5%) HBVMN patients demonstrated HBV DNA in the glomeruli and tubular epithelia. In contrast to the 14 HBVMN specimens taken later than 6 months after the onset, HBV DNA was detectable in only 3 (21%) in the tubular epithelia but none in the glomerular region. Most of the glomeruli-associated HBV DNA seemed extracellular because they were also positive for both the accumulation of HB e antigen (HBeAg)-anti-HBe antibody (Ab) immune complex and immunoglobulin G. The finding suggested that glomeruli-associated viral DNA is joined with filtered HBeAg-anti-HBeAb immune complexes. In the analysis of follow-up biopsies, HBV DNA in tubular epithelia was detected more frequently in the progressive group (50%) than in the nonprogressive group (0%). HBV DNA was detectable in the tubular epithelia in 2 cases who were progressing to end-stage renal disease and had heavy proteinuria. However, in the cases with mild or no proteinuria, HBV DNA was no longer detectable in the kidney. These findings suggest that HBV disseminates in the kidney and its dynamic changes at different time points may implicate the important role of HBV in the pathogenesis of HBVMN. This needs further study to be clarified.