Serum elastase-1, amylase, lipase, and trypsin-like immunoreactivity were measured in a group of 17 consecutive patients with acute pancreatitis. When assayed within 24 h of the onset of symptoms, all enzymes were found to be elevated, thus showing similar sensitivity. Elastase-1 did not improve the diagnostic score of the other enzymes studied. Owing to their much quicker and less expensive determinations, amylase and lipase should be considered the best initial markers of pancreatic injury. However, during the course of pancreatitis, amylase and in a lesser degree lipase returned to normal in more cases than elastase or trypsin; both were still elevated in 90% of the patients 10 days after the onset of the symptoms. Thus, trypsin and/or elastase-1 should be reserved for cases of doubtful or delayed diagnosis. The specificity and the positive predictive value of these enzymes need to be evaluated.