With the use of a precise and unique model, pancreatic secretion was studied in three humans who had chronic pancreatitis. The observed results show a decrease in pancreatic secretory pressure and volume during the administration of an elemental diet, Vivonex HN, compared with regular feedings. Levels of secretory function were near those observed during fasting in the two patients receiving the elemental diet. The variably low levels of enzyme activity observed during the administration of Vivonex HN suggest only minimal stimulation of cholecystokinin. It would seem that the primary inhibitory effect of the elemental diet may be more specifically related to a reduction of secretin release. Although the numbers of observations carried out during this study were small, the precise nature of the model being studied allows the conclusion that the administration of a low fat elemental diet to patients with chronic pancreatitis produces minimal stimulation of pancreatic secretion.