To evaluate the effect of azathioprine with steroids on the clinical course and histologic parameters of severe Henoch-Schönlein nephritis (HSN), 20 patients with a median age of 9.3 years (range 4.4-17 years) and a follow-up period of 4.8 years (range 1-14 years) were included in this study. The patients were divided into two groups. Ten patients received azathioprine with steroids for 8 months (group A), and the other ten received steroids alone (group B). All patients underwent renal biopsy at presentation, and ten of them who were treated with azathioprine underwent follow-up biopsy after therapy. Six patients in group A achieved clinical remission, and the remaining four showed minor urinary abnormalities at the latest observation. The histological grades of the International Study of Kidney Disease in Children (ISKDC) improved in four of the ten patients, and the activity index decreased significantly from 6.8+/-2.0 to 4.3+/-2.3 (p=0.016). In group B, however, four patients had normal urine and renal function; two had minor urinary abnormalities; one had active renal disease, and three had chronic renal insufficiency, at the latest observation. The combination treatment of azathioprine and steroids may be beneficial in ameliorating histopathological features and improving the clinical course of severe HSN.