Past studies concerning postoperative apnoea in infants were identified and reviewed. A total of only 200 former preterm infants having minor surgery under general anaesthesia have been prospectively studied. The incidence of apnoea after general anaesthesia is approximately 30%, and is inversely related to postconceptual age. A large number of term infants have been studied, and the incidence of postoperative apnoea is very low. The initial apnoea is always within 12 hours of surgery, though only one study has collected data beyond this length of time. Past history of apnoea episodes, bronchopulmonary dysplasia, anaemia or neurological disease may be associated with an increased risk, though current evidence is not strong. No patient characteristic apart from postconceptual age has enough sensitivity and specificity to identify a high-risk group. The use of spinal anaesthesia or methylxanthines may reduce the incidence of postoperative apnoea, but again the evidence is not strong. Recommendations concerning the timing of elective surgery and the use of postoperative respiratory monitoring in the former preterm infant can only be made cautiously in view of the paucity of data on which to base them.