Antineutrophil cytoplasmic autoantibodies, which are now considered reliable serological markers of acute necrotizing vasculitic diseases, were measured in 11 patients with acute necrotizing pancreatitis and 12 patients with acute interstitial pancreatitis. When tested by indirect immunofluorescence, none of the sera was positive for diffuse cytoplasmic staining, and none was positive for perinuclear staining of antineutrophil cytoplasmic antibodies. Also by the sensitive enzyme-linked immunosorbent assay, none of the sera was positive when purified alpha-granule fraction of granulocytes was used as an antigen. We can therefore conclude that neither the diffuse cytoplasm-reacting, nor the perinuclear form of antineutrophil cytoplasmic antibodies, is involved in cases of acute pancreatitis.