The aim of this study was to evaluate glomerular C3c deposits of Henoch-Schönlein purpura nephritis (HSPN) in children. Fifty-one patients aged 7-15 years (20 males and 31 females) were studied. On histological investigation, crescent formation seen under light microscopy and subepithelial electron dense deposits (EDD) under electron microscopy were found to be related to the degree of proteinuria and the duration of proteinuria and/or hematuria. A comparative clinicopathological study was performed on C3c-positive patients (n = 22) and C3c-negative patients (n = 25). Histological findings, such as crescent formation and subepithelial EDD, had no relation to glomerular C3c-deposits. At renal biopsy, C3c deposits were positive in 65 % of patients with heavy proteinuria ( > 100mg/kg/day), and in 30% of mild proteinuria patients ( < 50mg/kg/day). The difference between the two groups was statistically significant (p < 0.05). The duration of proteinuria and/or hematuria in C3c-positive patients had a tendency to persist in comparison with that in C3c-negative cases. Renal biopsies on many cases of C3c-negarive patients were performed following the lapse of three months, while the biopsies on patients showing global (+) C3c deposits (n = 15) were conducted within the three-month period. These results suggest that glomerular C3c deposits influence the clinical conditions of patients with HSPN, and complement activation is generated in the early stage of HSPN.