Oral rehydration therapy (ORT)--World Health Organisation formula--has reduced the mortality of severe diarrhoea tenfold but its use in Intensive Care has not been reported. ORT was administered via a nasogastric tube to 3 adult intensive care patients who developed severe diarrhoea and post-operative acute renal impairment. The median intake of ORT was 2.21/day (range 1.5-3.0) and the mean duration of therapy was 7 days (range 6-10). Renal function improved (creatinine fell from 389 to 165 mmol/l) and both haemodynamic and metabolic stability (Na, K, Mg, PO4 and urea) were maintained. While it may not reduce the volume of diarrhoea, ORT provides a cheap, effective and physiological solution to severe gastrointestinal losses in intensive care and may have wider application in both adult and paediatric practice.