A new definition of intestinal failure is of reduced intestinal absorption so that macronutrient and/or water and electrolyte supplements are needed to maintain health or growth. Severe intestinal failure is when parenteral nutrition and/or fluid are needed and mild intestinal failure is when oral supplements or dietary modification suffice. Treatment aims to reduce the severity of intestinal failure. In the peri-operative period avoiding the administration of excessive amounts of intravenous saline (9 g NaCl/l) may prevent a prolonged ileus. Patients with intermittent bowel obstruction may be managed with a liquid or low-residue diet. Patients with a distal bowel enterocutaneous fistula may be managed with an enteral feed absorbed by the proximal small bowel while no oral intake may be needed for a proximal bowel enterocutaneous fistula. Patients undergoing high-dose chemotherapy can usually tolerate jejunal feeding. Rotating antibiotic courses may reduce small bowel bacterial overgrowth in patients with chronic intestinal pseudoobstruction. Restricting oral hypotonic fluids, sipping a glucose-saline solution (Na concentration of 90-120 mmol/l) and taking anti-diarrhoeal or anti-secretory drugs, reduces the high output from a jejunostomy. This treatment allows most patients with a jejunostomy and > 1 m functioning jejunum remaining to manage without parenteral support. Patients with a short bowel and a colon should consume a diet high in polysaccharides, as these compounds are fermented in the colon, and low in oxalate, as 25% of the oxalate will develop as calcium oxalate renal stones. Growth factors normally produced by the colon (e.g. glucagon-like peptide-2) to induce structural jejunal adaptation have been given in high doses to patients with a jejunostomy and do marginally increase the daily energy absorption.