The term systemic vasculitis concerns a group of diseases characterized by inflammation of vessels. The diagnosis and follow-up of these conditions is a serious challenge since their classification is difficult and the therapy is usually empiric. Perhaps the greatest breakthrough in the management of these diseases is the recent discovery of serological markers for some vasculitic syndromes. Wishing to determine how far the tests for detection of these antibodies are specific, sera from 63 patients with systemic vasculitides were tested by immunofluorescence of ethanol fixed neutrophils. Two different staining patterns were observed. The cytoplasmic staining (classic pattern) was very specific for Wegener's granulomatosis. In contrast, the perinuclear staining was also present in many vasculitic syndromes such as microscopic polyarteritis and poliarteritis nodosa. In addition, the sera were tested by ELISA, using whole neutrophil cell extract. Although the assay was less specific than the immunofluorescence, the test was helpful in discriminating between true ANCA and atypical fluorescence patterns. Moreover, high levels of antimieloperoxidase antibodies detected by ELISA in a limited number of patients were exclusively associated with the diagnosis of microscopic polyarteritis or Wegener's granulomatosis with renal involvement. Our data confirm the remarkable association of antineutrophil cytoplasmic antibodies with vasculitic syndromes.(ABSTRACT TRUNCATED AT 250 WORDS)