OBJECTIVE Pauci-immune crescentic glomerulonephritis (CrGN) is frequently associated with circulating anti-neutrophil cytoplasmic antibodies (ANCA). However, in patients with ANCA-negative pauci-immune CrGN, the pathogenesis is not clear. Anti-endothelial cell antibodies (AECA) have been implicated in the pathogenesis of vasculitis. The purpose of this study is to investigate the prevalence of AECA and their possible clinical significance in ANCA-negative pauci-immune CrGN. METHODS Sera from 19 patients with ANCA-negative pauci-immune CrGN, 26 patients with ANCA-positive pauci-immune CrGN and 10 healthy blood donors were collected. Soluble proteins extracted from cultured human umbilical vein endothelial cells were used as antigens and western blot analysis was carried out to detect AECA. RESULTS In ANCA-negative pauci-immune CrGN, 10 of 19 patients were serum IgG-AECA positive and seven bands reactive with endothelial antigens could be blotted. The prevalence of skin rash and thrombocytosis was significantly higher in patients with anti-76 kDa and anti-123 kDa autoantibodies than in patients without, respectively. Birmingham Vasculitis Activity Scores of patients with anti-200 kDa AECA were significantly higher than in patients without. In the sera of 26 ANCA-positive cases, 23 were AECA positive and 11 bands could be recognized. The prevalence of total AECA and anti-90 kDa AECA was significantly lower in patients with ANCA-negative pauci-immune CrGN than in patients with ANCA-positive pauci-immune CrGN. CONCLUSIONS Anti-endothelial cell antibodies could be found in sera of patients with ANCA-negative pauci-immune CrGN; some AECA might have some clinical significance. The discrepancies of AECA might be a possible contributor to the differences between ANCA-negative and ANCA-positive pauci-immune CrGN.