Adult mongrel dogs were fed during 8 days on one of two diets, one rich in fat (FR) and the other rich in carbohydrates (CR), in order to compare the exocrine pancreatic secretion in the basal period and in response to food. Under resting conditions, mean pancreatic juice flow and mean values of protein content, amylase and lipase activity and production were similar in both experimental groups, suggesting that the period of adaptation used did not produce any influence on the measured parameters. No significant difference between the two dietary groups was found in postprandial volume of pancreatic juice. The peak of pancreatic juice flow in FR-group was smaller but remained elevated until the end of the 5th h, possibly due to the fact of delayed gastric emptying when animals are fed with a high fat diet. No significant differences were found between the groups in neither postprandial amylase activity and secretion nor lipase activity. On the other hand, lipase output was significantly higher in FR-group but only during the 5 postprandial h. This fact may be related to some intestinal factor stimulated by the hydrolysis products of fat. Finally, our findings show that no rapid adaptation of exocrine pancreatic secretion exist to the diet, at least in our experimental conditions. Of course, this does not exclude that the phenomenon of adaptation may appear in the dog under long-term adaptation to the diet.