We report on a 10-year-old girl with glomerulonephritis associated with hepatitis C virus infection, who was treated with interferon-alpha. On the first renal biopsy at 8 years of age, mild mesangial hypercellularity in a segmental to semiglobal pattern was present in all glomeruli. After 6 months interferon-alpha therapy, proteinuria diminished completely. However, mesangial proliferation was advanced on the second biopsy at 10 years of age. We concluded that the interferon-alpha was effective in the treatment of proteinuria despite the lack of pathological improvement.