Anti-glomerular basement membrane (GBM) antibodies were induced in the Brown-Norway rat by mercuric chloride. The existence of anti-GBM antibodies was suspected because of the immunofluorescent linear pattern. It was proved because eluted antibodies from kidneys and circulating IgG had an anti-glomerular basement membrane activity. A glomerular basement membrane antigen modified by HgCl2 is probably responsible for the appearance of such antibodies. The previous demonstration of the occurrence of an immun complex type glomerulonephitis, in outbred Wistar rats, under the same experimental conditions, suggests the existence of a genetic control for this type of immune response.