Reports on pancreatic enzyme secretion during acute pancreatitis are sparse and contradictory. In this study pancreatitis was induced by injection into the pancreatic ducts of sodiumtaurodeoxycholate (NaTDC) and trypsin, and the effect on secretory volume, protein, amylase and bicarbonate secretion was studied. In healthy rats the pancreatic secretion was stable throughout the experimental period. Induction of pancreatitis caused a marked reduction of both secretory volume and protein output of pancreatic juice. Exogenous hormonal stimulation by secretin, cerulein or a combination of both hormones did not affect volume or protein output. Also when measuring bile-pancreatic juice, pancreatitis caused a significant reduction of secretory volume and a gradual decrease of protein output. Amylase output was rapidly and markedly reduced, whereas bicarbonate output was unaffected by the induction of pancreatitis. Pancreatographic studies showed that the impaired secretion was rather a result of ductal and parenchymal injury than of ductal obstruction. Thus, the results of the present study suggest that pancreatic enzyme secretion is markedly reduced during acute experimental pancreatitis. The findings should be considered when evaluating present therapeutic measures and when searching for new ones in acute pancreatitis.