Complexes of granulocyte elastase and alpha 1-antitrypsin are markers for granulocyte activation. In 75 patients with acute pancreatitis these complexes were immunologically determined daily in plasma during the first week of hospitalization. Patients were classified into three groups: mild pancreatitis (I, less than or equal to 1 complication, N = 34), severe pancreatitis (II, greater than or equal to 2 complications, N = 29), lethal outcome (III, N = 12). Initially, granulocyte elastase (mean +/- SEM) was lower in group I (348 +/- 39 micrograms/liter) as compared to groups II (897 +/- 183 micrograms/l) and III (799 +/- 244 micrograms/liter), P less than 0.001 for I vs II + III. Initial elastase concentrations greater than 400 micrograms/liter were consistent with a severe or fatal course of the disease but did not distinguish between severe and lethal pancreatitis. In patients with mild or severe disease, mean elastase concentrations decreased continuously during the following days (197 +/- 15 micrograms/liter in mild cases, 325 +/- 30 micrograms/liter in severe cases at day 7). In patients with lethal disease, however, mean elastase concentrations even increased at day 2 and remained higher than 700 micrograms/liter during the observation period. At days 1 and 2 the predictive value for severe or lethal disease of raised (greater than 400 micrograms/liter) elastase concentrations [positive predictive value (PPV) 82%, negative predictive value (NPV) 81%] was better than that of elevated (greater than 100 mg/liter) C-reactive protein (PPV 73%, NPV 73%), elevated (greater than 4.0 g/liter) alpha 1-antitrypsin (PPV 59%, NPV 50%), or decreased (less than 1.5 g/liter) alpha 2-macroglobulin (PPV 82%, NPV 67%).(ABSTRACT TRUNCATED AT 250 WORDS)