Experimental autoimmune glomerulonephritis (EAG) can be induced in Wistar Kyoto (WKY) rats by immunization with the non-collagenous domain (NC1) of the alpha 3 chain of type IV collagen, α3(IV)NC1. In patients with Goodpasture's disease, the major B cell epitope is located at the N-terminus of α3(IV)NC1. In order to investigate whether B and T cell responses in EAG are directed towards immunodominant peptides within the same region of rat α3(IV)NC1, we immunized WKY rats with recombinant rat α3(IV)NC1 (positive control) and five 15-mer overlapping synthetic peptides from the N-terminus of rat α3(IV)NC1: pCol(17–31), pCol(24–38), pCol(31–45), pCol(38–52) and pCol(45–59). Positive control animals immunized with α3(IV)NC1 produced an antibody response directed towards α3(IV)NC1 and pCol(24–38). Splenic T cells from these animals proliferated in response to α3(IV)NC1 and pCol(24–38). No significant antibody or T cell responses were observed to the other peptides examined. Animals immunized with pCol(24–38) developed linear deposits of immunoglobulin G on the glomerular basement membrane, albuminuria and focal necrotizing glomerulonephritis with crescent formation by week 6 after immunization. Circulating antibodies from these animals recognized pCol(24–38) and α3(IV)NC1, and their T cells proliferated in response to pCol(24–38) and α3(IV)NC1. Animals immunized with the other peptides developed no significant immune response to α3(IV)NC1 and no disease. In conclusion, these results demonstrate that a 15-mer peptide from the N-terminus of α3(IV)NC1 [pCol(24–38)] is recognized by B and T cells from rats immunized with recombinant α3(IV)NC1, and that the same peptide is capable of inducing crescentic glomerulonephritis. Identification of this immunodominant peptide will be of value in designing new therapeutic strategies for inducing mucosal tolerance in EAG, which may be applicable to patients with glomerulonephritis.