This study describes the effect on the function and structure of the saline-perfused cat pancreas of factors implicated in the pathogenesis of pancreatitis (bile acid, ethanol, pancreatic enzymes) after their addition to the perfusion fluid or their instillation into the pancreatic duct. Instillation of trypsin or chenodeoxycholic acid, but not ethanol, into the pancreatic duct resulted in a profound suppression of secretory function. The leakage of perfusion fluid and amylase from the gland was also abruptly increased. Intraarterial perfusion of trypsin also inhibited secretin-induced flow and cholecystokinin evoked enzyme secretion. Intraarterial bile acid inhibited fluid flow but augmented enzyme secretion in a concentration-dependent manner. In addition, massive or focal parenchymal necrosis was caused by sustained intraarterial perfusion of bile acid or trypsin, respectively. Elastase and phospholipase A had little influence on pancreatic function or structure when added to the perfusion fluid. These findings show that pancreatic structure and function can be disturbed by potentially toxic factors administered not only via the ductal system but also via the vascular route, and consequently suggest that an "internal reflux" mechanism could be involved in the pathogenesis of pancreatitis in addition to a "ductal reflux" mechanism.