Serologic tests for antineutrophil cytoplasmic autoantibodies can serve as markers fora number of necrotizing vasculitides and other inflammatory disorders. In the case of Wegener's granulomatosis, an immunofluorescent cytoplasmic pattern and immunoassay for proteinase 3 are quite specific for the disease and are capable of serving as additional criteria for diagnosis. As with any laboratory test, however, results are to be interpreted in the whole clinical and pathologic framework of the disease.