It has been reported that somatostatin may be an effective antisecretory agent in a range of conditions causing severe secretory diarrhoea. In many children, intractable diarrhoeal illnesses result in significant morbidity and mortality. In a group of seven children with secretory diarrhoea, the effect of i.v. infusion of somatostatin (3.5 micrograms/kg stratum plus 3.5 micrograms/kg/h) on the net mucosal flux of salt and water was assessed using an in vivo steady-state perfusion technique. In one of the seven children who had evidence of deranged mucosal secretion and preserved villus function, somatostatin infusion resulted in a moderate reduction in secretion. In the remaining six, it had little or no beneficial effect. Somatostatin did not alter the rate of glucose absorption.