Purpose : To report the decreasing indicence of HBV(Hepatitis B virus)-associated membranous nephropathy in children after HBV vaccination and to elucidate the clinical course and treatment strategies of IMN(Idiopathic membranous nephropathy). Methods : We retrospectively reviewed the clinico-pathological findings of HBV-MN and IMN patients who underwent a renal biopsy from 1986 to 2005. We compared the HBV-MN and the IMN groups and the remission and the non-remission groups of patients with IMN. Results : Among 24 cases of MN patients, HBV-MN comprised 6 cases(25%) and IMN 18 cases(75%). Clinical masnifestations were nephrotic syndrome(3 cases, 50%), nephritic syndrome(1 case, 16.7%), asymptomatic(2 cases, 33.4%) in the HBV-MN group, asymptomatic(10 cases, 55.5%), nephrotic syndrome(5 cases, 27.8%), and gross hematuria(3 cases, 16.7%) in the IMN groups. From 1996 to 2000, there were 2 cases(28%) of HBV-MN and 5 cases(72%) of IMN. After 2001 all 10 cases were IMN. In the HBV-MN group, 4 cases(66.7%) received interferon and 1 cases received methylprednisolone pulse therapy. In the IMN group, 16 cases(88.9%) received methylprednisolone, 8 cases(44.4%) were in complete remission, 2 cases(11.1%) were in partial remission, 2 cases(11.1%) were in chronic renal failure, and 5 cases(27.8%) were lost to follow-up with sustained proteinuria, 1 case(5.6%) continued to have frequent relapse of nephrotic syndrome without renal insufficiency. In the comparison between remission and non-remission groups, nephrotic range proteinuria and hypertension were more significantly common in the non-remission group(P<0.05). Conclusion : With HBV vaccination, HBV-MN has decreased markedly. IMN is a rare glomerular disease in children. Because the prognosis for patients with nephrotic range proteinuria is poor this group needs more aggressive treatment.