Three patients with acute pancreatitis diagnosed while they were taking enalapril are described. In two of these patients, enalapril was the only drug taken immediately before the symptoms began, and other etiologies were accurately excluded. In the third patient, the relationship between enalapril and acute pancreatitis was shown by a rechallenge with the drug that resulted in severe acute pancreatitis. This report is a definite demonstration of the relationship between enalapril and acute pancreatitis. We suggest stopping treatment with enalapril in patients suspected of having acute pancreatitis. We also recommend not rechallenging patients with the drug because of the risk of inducing severe acute pancreatitis.