We evaluated whether methylprednisolone and urokinase pulse therapy combined with mizoribine (MUPM) was effective in children with severe Henoch-Schoenlein purpura nephritis (HSPN). We studied 12 patients who had been diagnosed with HSPN of at least ISKDC type III. All patients were treated with MUPM. Clinical features, pathological findings, and prognosis were prospectively investigated. Ten patients (responders; nine with ISKDC grade IIIb and one with grade IVb) were treated with MUPM, whereas MUPM was discontinued due to the lack of response in two patients (non-responders; two with grade IVb). Among responders, urinary protein excretion had decreased significantly from 99.7 ± 37.8 to 25.9 ± 33.4 mg/m(2) per hour after 3 months of therapy. The acute index and tubulointerstitial scores decreased significantly from 5.8 ± 1.5 and 3.8 ± 0.6 at the first biopsy to 2.3 ± 1.3 and 1.0 ± 0.8 at the second biopsy, respectively. At the most recent follow-up, eight of the responders had normal urine, and two had minor urinary abnormalities. Non-responders demonstrated continued high levels of urinary protein excretion after 3 months of therapy, and MUPM was discontinued. Our study suggests that MUPM is effective in ameliorating the proteinuria and the histological severity of HSPN in patients with <50% crescents but is not so effective for HSPN in patients with >50% crescents.