A survey was conducted in a sample of 29 pharmacies in the Badinh district of Hanoi, Vietnam, to determine the knowledge and behaviour of pharmacy staff in dealing with cases of acute diarrhoea in children. The survey found that antibiotics and antidiarrhoeal drugs were suggested in the majority of cases (45 per cent and 69 per cent, respectively) while oral rehydration salts (ORS) were suggested in only one case. In about 80 per cent of the observed cases in which antibiotics were supplied, one to four tablets were given, enough for only one to two days. The advice given by pharmacy staff to purchasers was poor. Only about half the pharmacy staff asked for information about the stool, age of the child and frequency of diarrhoea, while questions about medicines that had already been taken, feeding and health status were rarely asked. In about 10 per cent of the cases, no questions at all were asked. The mean cost of the treatment was $ 0.53 (95 per cent CI = 0.37–0.68). Constraints of knowledge, time and finance could be the reasons for this inappropriate management of childhood diarrhoea.