Acute pancreatitis was induced in pigs by retrograde injection of Na-taurocholate into the pancreatic duct. Chromogenic peptide substrate assays showed increased trypsin (TRY) and plasma kallikrein activity (KK), parallel with a reduction of plasma prekallikrein (PKK) and functional kallikrein inhibition (KKI) values, in the peritoneal exudate in untreated animals. Intravenous high-dose pretreatment or therapy with aprotinin starting 3 h after the induction of acute pancreatitis resulted in significantly increased KKI capacity and unchanged KK and TRY activities in the peritoneal exudate. In test animals receiving aprotinin intravenously a significantly increased survival rate and improved cardiac output and arterial blood pressure were found during the 6-h observation period. All animals treated with aprotinin survived the observation period, whereas 63% of the untreated animals died. The study emphasizes the pathophysiological importance of the plasma kallikrein-kinin system in acute pancreatitis.