We investigated the clinical features and outcome of 60 patients with antineutrophil cytoplasmic autoantibodies with cytoplasmic staining (C-ANCA)- and with (peri)nuclear staining (P-ANCA)-associated glomerulonephritis. Virtually all patients with C-ANCA had antibodies against proteinase 3, which corresponded with a clinical and/or histological diagnosis of Wegener's granulomatosis (WG). P-ANCA were associated with antibodies against myeloperoxidase. Although more often associated with renal-limited disease, a significant number of patients with P-ANCA had also symptoms of organs known to be preferentially affected with WG. The majority of patients presented with rapidly progressive glomerulonephritis which responded favorably to immunosuppressive therapy, albeit at the expense of a considerable number of fatal infections. Furthermore, a more protracted form of glomerulonephritis was recognized. A kidney biopsy scoring system appeared to be of value in predicting which patients would benefit most from treatment. C-ANCA and P-ANCA appear to identify a subset of patients with vasculitis that share common clinical features and a favorable response to immunosuppressive therapy.