Cholecystokinin (CCK) has been suggested to be involved in the pathogenesis of acute pancreatitis. To test this hypothesis, we administered the highly selective and specific CCK receptor antagonist L 364,718 to rats in which acute experimental pancreatitis had been induced by the use of transduodenal pancreatic duct injection of taurocholate. It was, however, found that despite the use of L 364,718 at a high dose level (1 mg/kg body weight given three times), and also given prior to induction of pancreatitis, the mortality rate, the serum or ascites amylase activity, the pancreatic concentrations of lysosomal enzymes or the morphology of the pancreas were not affected. This suggests that the CCK receptors are not involved in the pathogenesis of acute pancreatitis in this experimental model, and, consequently, that CCK receptor antagonists have no place in the therapy of this condition.