To compare the clinical efficacy of oral rehydration salts (ORS) from effervescent tablets containing citrate with the WHO recommended ORS for the treatment of dehydration due to acute diarrhoea, a randomized clinical trial was carried out in 57 adults and 58 children. These patients had mild or moderate degrees of dehydration and acidosis due to acute watery diarrhoea that was caused by enterotoxigenic Escherichia coli in 43-47% of the cases. Efficacies were compared by measuring oral fluid intake, stool output, gain in body weight, decrease in serum specific gravity and correction of acidosis during treatment. Successful rehydration and maintenance of hydration was achieved in 25 adults and 24 children treated with citrate containing ORS and 25 adults and 24 children treated with WHO ORS. The mean intake of ORS/kg body weight in children receiving WHO ORS was greater (p less than 0.05) and correction of acidosis was faster than the citrate group during the initial 24 h of therapy (p less than 0.05). By 48 h, however, both groups showed satisfactory and comparable intake of ORS and correction of acidosis. Thus ORS from effervescent tablets containing sodium citrate base is effective for management of diarrhoea in both adults and children and is a convenient stable form of ORS for use in the home and for travelers.