Lung function was studied in 20 children, aged 8-17 years, who had successfully repaired oesophageal atresia with tracheo-oesophageal fistula. Spirometry and plethysmography showed mild restrictive lung disease. Airways obstruction was assessed using maximal expiratory and inspiratory flow-volume loops in air and after breathing a helium-oxygen mixture. Analysis of the flow-volume data demonstrated significant obstruction at the level of the trachea and little evidence of small airways disease. Bronchial hyperreactivity, as assessed by histamine challenge, was present in 22% of subjects. Respiratory and oesophageal symptoms were common, but decreased in frequency with increasing age. The mechanisms involved in the frequent respiratory symptoms these children suffer are discussed in the light of the physiological findings.