Documentation of Wegener's granulomatosis based on clinical characteristics and histopathologic and/or angiographic evidence of vasculitis. In the absence of histopathologic and/or angiographic evidence of vasculitis, patients who meet one of the following criteria and in whom infectious and autoimmune diseases that may mimic Wegener's granulomatosis or a related systemic vasculitides have been excluded will also be eligible: a) a positive assay for anti-neutrophil cytoplasmic autoantibodies (C- or P-ANCA) and the presence of glomerulonephritis defined by red blood cell casts and proteinuria or renal biopsy showing necrotizing glomerulonephritis in the absence of immune deposits; b) a positive assay for anti-neutrophil cytoplasmic autoantibodies (C- or P-ANCA) and the presence of granulomatous inflammation on biopsy plus abnormal chest radiograph (defined as the presence of nodules, fixed infiltrates, or cavities) plus nasal/oral inflammation on clinical examination.