We analyzed the role of polymorphonuclear granulocytes (PMN)-elastase in predicting the prognosis of patients with acute pancreatitis in comparison with C-reactive protein (CRP), lactate dehydrogenase (LDH), and the two antiproteases alpha 1-antitrypsin (alpha 1-AT) and alpha 2-macroglobulin (alpha 2-M). Fifty-two patients with acute pancreatitis were subdivided according to morphological criteria into 29 patients with edematous pancreatitis and 23 patients with necrotizing pancreatitis. Within 5 days after the onset of acute pancreatitis, the accuracy rates for detecting necrotizing pancreatitis were 86%, 84%, 82%, 72%, and 69%, using cutoff levels of 120 mg/L for CRP, 120 micrograms/L for PMN-elastase, 270 U/L for LDH, 1.5 g/L for alpha 2-M, and 3.5 g/L for alpha 1-AT, respectively. The median peak value of PMN-elastase was reached on day 1 of acute pancreatitis in contrast to the median peak of CRP, which was at its highest between days 3 and 4. PMN-elastase represents a reliable indicator, comparable with CRP, for the staging of acute pancreatitis. The advantage of PMN-elastase over CRP appears to be its earlier increase and the greater dynamism of its serum course. Finally, the results suggest that CT scanning for the evaluation of the extent of intra- and extrapancreatic necrosis could be restricted to those patients with increased values of PMN-elastase and CRP.