A randomized double blind controlled clinical trial was conducted on 30 patients with cholera and 18 patients with severe non-cholera diarrhoea, to study the antisecretory effect of acetylsalicylic acid (aspirin). The criteria for selection of patients was a stool output of 4 ml/kg per hour over 6 hours of baseline observation. On inclusion into the study, the groups were comparable in sex, age, body weight, duration of diarrhoea and severity of dehydration. Aspirin and placebo (starch) were given by mouth in doses of 25 mg/kg/day for 24 hours in four equally divided doses. Fourteen patients with cholera and 10 with non-cholera diarrhoea received aspirin and the others received placebo. The aspirin and the placebo groups did not differ in their rate of stool output. The results suggest that aspirin in the above mentioned dose has no antisecretory activity.