Two recent trials of angiotensin II receptor blockers (ARBs) were performed in children 0–5 years of age. Data from the published reports of these trials together with additional information from the sponsoring drug companies were obtained. Three deaths occurred in the 183 (1.6%) hypertensive children participating in the two trials. At least two of these deaths occurred in children known to be susceptible to drugs acting on the renin–angiotensin system, that is, children with ongoing nephrotic syndrome and acute gastroenteritis. Clinicians who prescribe ARBs in preschool children need to be aware of the risk of drug toxicity especially in children susceptible to intravascular dehydration. Clinicians should consider discontinuing the drugs in the presence of acute diarrhoea.