Patients with a high-output stoma (HOS) (> 2000 ml/day) suffer from dehydration, hypomagnesaemia and under-nutrition. This study aimed to determine the incidence, aetiology and outcome of HOS.The number of stomas fashioned between 2002 and 2006 was determined. An early HOS was defined as occurring in hospital within 3 weeks of stoma formation and a late HOS was defined as occurring after discharge.Six-hundred and eighty seven stomas were fashioned (456 ileostomy/jejunostomy and 231 colostomy). An early HOS occurred in 75 (16%) ileostomies/jejunostomies. Formation of a jejunostomy (defined as having less than 200 cm remaining of proximal small bowel; n = 20) and intra-abdominal sepsis? obstruction (n = 14) were the commonest causes identified for early HOS. It was possible to stop parenteral infusions in 53 (71%) patients treated with oral hypotonic fluid restriction, glucose-saline solution and anti diarrhoeal medication. In 46 (61%) patients, the HOS resolved and no drug treatment was needed, 20 (27%) patients continued treatment, six (8%) of whom went home and continued to receive parenteral or subcutaneous saline, and nine died. Twenty-six patients had late HOS. Eleven were admitted with renal impairment and four had intermittent small-bowel obstruction. Eight patients were given long-term subcutaneous or parenteral saline and two also received parenteral nutrition. All had hypomagnesaemia.Early high output from an ileostomy is common and although 49% resolved spontaneously, 51% needed ongoing medical treatment, usually because of a short small-bowel remnant.