Animal experimental data concerning pancreatic exocrine secretory response to parenteral nutrition is contradictory. We have studied the pancreatic exocrine output in a patient with a pure pancreatic fistula. In this patient, parenteral nutrition with hypertonic glucose, amino acids and fat emulsion was not associated with increases in fistula volume or protein output. Enteral protein and fat in this patient caused rapid increases in both fistula volume and protein output. This study supports the use of parenteral nutrition as a means of maintaining the pancreas at rest.(Journal of Parenteral and Enteral Nutrition8:34–36, 1984)