Objective To determine the prevalence of autoantibodies against glomerular basement membrane(GBM) in sera of Chinese patients with rapidly progressive glomerulonephritis(RPGN)and to evaluate their clinical relevance. Methods Serum anti-GBM antibodies were detected in 29 RPGN patients by enzyme-linked immunoassay(ELISA)using collagenase solublized human GBM as solid phase ligand. Positive sera were also oonfirmed by Western blot analysis. Results Of the 29 RPGN patients, 5(17%)were positive for anti-GBM autoantibodies. One positive for both anti-GBM autoantibody and ANCA. On Western blot analysis. 23 000～27 000 and 40 000～54 000 polypeptides could be blotted. On direct immunofluoresence there were granular deposits of immunocomplex in capillary loops in three of four. Conclusions The prevalence of anti-GBM antibody mediated RPGN is not rare in China. Using ELISA to detect circulating anti-GBM autoantibodies had been proved to be a more specific and sensitive methods. It is important to detect circulating anti-GBM autoantibodies early for patients with RPGN in order to save time for appropriate therapy.