Remifentanil hydrochloride is an ultra-short-acting opioid that undergoes rapid metabolism by tissue and plasma esterases. Remifentanil is increasingly used as an adjuvant to general anaesthesia in neonates undergoing surgery because of its favourable haemodynamic and respiratory effects compared with other agents. The pharmacokinetic profile of remifentanil appears well suited for use in the sedation of children for short, day case procedures and remifentanil has been demonstrated to be an attractive drug for this purpose. Owing to higher clearances, younger children will require higher infusion rates of remifentanil than older children and adults to achieve equivalent plasma concentrations. Propofol and remifentanil appear to be gaining popularity for short procedures in children. Together they provide sedation, anxiolysis and analgesia, possibly best provided by separate continuous infusions. They also promote haemodynamic stability, minimal respiratory depression, with a rapid recovery profile. The use of remifentanil in neonates and young infants is increasing despite the difficulties in obtaining high standard objective evidence in this age group. Remifentanil’s pharmacokinetic and pharmacodynamic profile in this age group is similar to that of older children, which may have several theoretical advantages. Reports of a rapid development of µ-receptor tolerance with remifentanil are in conflict; activity at δ-opioid receptors may contribute. Remifentanil produce a fall in blood pressure and cardiac index, mainly as a result of a fall in heart rate. Although atropine is able to reduce the fall in heart rate, is not able to prevent completely the reduction in cardiac index. Remifentanil has been described as a titratable opioid. It has been reported to be ideally suited to the sedation of selected neurosurgical patients who require frequent neurological examinations. It may also provide suitable analgesia based sedation in mechanically ventilated children postoperatively.