Assessment of the severity of acute pancreatitis (AP), together with the patient's nutritional status is crucial in the decision making process that determines the need for artificial nutrition. Both should be done on admission and at frequent intervals thereafter. The indication for nutritional support in AP is actual or anticipated inadequate oral intake for 5-7days. This period may be shorter in those with pre-existing malnutrition. Substrate metabolism in severe AP is similar to that in severe sepsis or trauma. Parenteral amino acids, glucose and lipid infusion do not affect pancreatic secretion and function. If lipids are administered, serum triglycerides must be monitored regularly. The use of intravenous lipids as part of parenteral nutrition (PN) is safe and feasible when hypertriglyceridemia is avoided. PN is indicated only in those patients who are unable to tolerate targeted requirements by the enteral route. As rates of EN tolerance increase then volumes of PN should be decreased. When PN is administered, particular attention should be given to avoid overfeeding. When PN is indicated, a parenteral glutamine supplementation should be considered. In chronic pancreatitis PN may, on rare occasions, be indicated in patients with gastric outlet obstruction secondary to duodenal stenosis or those with complex fistulation, and in occasional malnourished patients prior to surgery.