The following are some of the conclusions and proposals made at the Chapel Hill Consensus Conference on the Nomenclature of Systemic Vasculitis. 1. Although not a prerequisite component of the definitions, patient age is recognized as a useful discriminator between Takayasu arteritis and giant cell (temporal) arteritis. 2. The name "polyarteritis nodosa," or alternatively, the name "classic polyarteritis nodosa," is restricted to disease in which there is arteritis in medium-sized and small arteries without involvement of smaller vessels. Therefore, patients with vasculitis affecting arterioles, venules, or capillaries, including glomerular capillaries (i.e., with glomerulonephritis), are excluded from this diagnostic category. 3. The name "Wegener's granulomatosis" is restricted to patients with granulomatous inflammation. Patients with exclusively nongranulomatous small vessel vasculitis involving the upper or lower respiratory tract (e.g., alveolar capillaritis) fall into the category of microscopic polyangiitis (microscopic polyarteritis). 4. The term "hypersensitivity vasculitis" is not used. Most patients who would have been given this diagnosis fall into the category of microscopic polyangiitis (microscopic polyarteritis) or cutaneous leukocytoclastic angiitis. 5. The name "microscopic polyangiitis," or alternatively, "microscopic polyarteritis," connotes pauci-immune (i.e., few or no immune deposits) necrotizing vasculitis affecting small vessels, with or without involvement of medium-sized arteries. Cryoglobulinemic vasculitis, Henoch-Schönlein purpura, and other forms of immune complex-mediated small vessel vasculitis must be ruled out to make this diagnosis. 6. The name "cutaneous leukocytoclastic angiitis" is restricted to vasculitis in the skin without involvement of vessels in any other organ. 7. Mucocutaneous lymph node syndrome must be present to make a diagnosis of Kawasaki disease.(ABSTRACT TRUNCATED AT 250 WORDS)