Nine Japanese children with severe proteinuric Henoch-Schönlein purpura nephritis (HSPN) received prompt initiation of oral prednisolone (1.5 mg/kg/day) combined with an 8-week course of cyclophosphamide (2 mg/kg/day) therapy. All underwent renal biopsy before and after treatment. At presentation, urine protein excretion and histologic indices of the mean activity index, the mean chronicity index and the tubulointerstitial (TI) scores in the patients were 5.0+/-1.4, 4.7+/-1.0, 3.9+/-1.6 and 3.7+/-0.5 g/day, respectively. Urine protein excretion, the activity index and the TI scores decreased significantly at the second renal biopsies obtained at a mean interval of 23 months after the first [0.3+/-0.3, 2.4+/-0.5 and 1.4+/-0.7 g/day ( P<0.01), respectively], while the chronicity index did not change. At the latest observation (mean interval 78 months), all except two showed negative proteinuria while no patient showed renal impairment. Although this case series is without controls, our experience suggests that early treatment with oral prednisolone and cyclophosphamide may be beneficial to a proportion of patients with severe proteinuric HSPN.