A controlled, randomised trial comparing the results of oral rehydration therapy with those of intravenous fluid treatment in 470 children with severe gastroenteritis was undertaken. The oral rehydration therapy was divided into two phases--a rehydration phase that used high sodium isotonic fluid at 40 ml/kg per hour and a maintenance phase using low sodium isotonic fluid (sodium 40, potassium 30, bicarbonate 25, chloride 45, and dextrose 130 mmol/l). The results indicate that oral rehydration treatment, used according to this protocol, is successful in treating severe diarrhoea and dehydration, and has considerable advantages over intravenous fluid therapy in reducing complications associated with the treatment of hypernatraemia, in promoting rapid correction of hypokalaemia and acidosis, in decreasing the duration of diarrhoea, and in promoting a greater weight gain at hospital discharge.