A prospective survey of anaesthesia-related mortality and morbidity in infants and children was carried out in a representative sample of anaesthetics performed in 440 institutions chosen at random in France. A total of 40240 anaesthetics were administered to patients younger than 15 yr, 2103 (5%) involving infants (younger than 1 yr). Twenty-seven major complications related to anaesthesia occurred during or within 24 h of the anaesthesia—an incidence of 0.7 per 1000 anaesthetics. Nine, of which four were associated with cardiac arrest, were observed in infants, whereas in children there were 18 complications of which eight were associated with cardiac arrest, one with fatal outcome. The risk of complications was significantly higher (P < 0.001) in infants (4.3 per 1000) than in children (0.5 per 1000). Accidents observed in infants mainly occurred during maintenance of anaesthesia and were the result of respiratory failure. In children, circulatory failure was as frequent as respiratory failure and complications were observed almost equally during induction and maintenance and on recovery. The rate of complications increased significantly with the ASA score and the number of co-existing diseases. The incidence was also higher when a previous history of anaesthesia was present, when the procedure was an emergency, and when the duration of preoperative fasting was less than 8 h.