Nutritional support, whether enteral or parenteral, is an important part of the treatment of IBD. Inadequate oral intake, malabsorption, and increased gastrointestinal losses all contribute to malnutrition. Weight loss, cachexia, abnormal body composition, and multiple micronutrient deficiencies are common. Acute repletion of body weight and correction of specific nutrient deficiencies improve the patients' sense of well-being and decrease morbidity, especially in the perioperative period. If a short period of bowel rest (10 to 14 days) is part of the medical therapy of acute exacerbations of IBD, TPN should be administered to prevent further nutritional deficiencies. Chronic undernutrition, and growth failure in children, usually are best treated by intensive enteral supplementation. Prolonged bowel rest and TPN (4 to 6 weeks) have not been shown to improve outcome but may be appropriate in carefully selected patients. Long-term home TPN may be necessary for patients who have short gut syndrome. The mainstay of treatment for IBD is medical therapy including corticosteroids. Timely and appropriate surgery is equally important and should not be considered a last resort. Careful nutritional management is essential but is adjunctive rather than primary therapy.