Patients 10 to 80 years of age with active Wegener's granulomatosis, polyarteritis nodosa, Churg-Strauss vasculitis, or microscopic polyangiitis overlap may be eligible for this 2 1/2 to 3-year study. In addition, patients with glomerulonephritis (a type of kidney disease) and a positive blood test for C-ANCA (antibodies found in certain vasculitic kidney diseases) or inflammatory sinusitis or lung nodule or infiltrates in the absence of infection may also be enrolled.