Serum pancreatic elastase 1 content in 45.9% of 203 samples from 32 patients with acute pancreatitis was found to be greatly elevated to greater than 1000 ng/dl, much higher than the control values (90 to 270 ng/dl), whereas serum alpha-amylase activity, in 62.3% of the same samples, was within the control range (100 to 460 IU/L). The increased pancreatic elastase 1 content persisted for several days after serum alpha-amylase activity returned to normal, suggesting that, compared with serum alpha-amylase activity, pancreatic elastase 1 content truly reflects the clinical course of acute pancreatitis. The measurement of pancreatic elastase 1 content appears to be more valuable in the diagnosis and prognosis of acute pancreatitis than that of serum alpha-amylase activity. In 41 patients with chronic pancreatitis, on the other hand, pancreatic elastase 1 content and serum alpha-amylase activity were within the normal range in 38.3% and 56.2% respectively, of 336 samples.