Postoperative respiratory complications are the commonest problem after all types of thoracic surgery. The exact incidence depends on the type of surgery and the preoperative health and lung function of the patient, but rates of up to 50% are often quoted. 12 Most of these complications are diagnosed as either ‘pneumonia’ or ‘postoperative atelectasis’. However, the role of microbiological pathogens is often uncertain and the diagnosis of atelectasis usually rests on the presence of shadowing on the postoperative chest x-ray. This article will discuss a specific type of severe respiratory problem that occurs after thoracotomy, namely the syndrome of acute lung injury (ALI). The features of lung injury after thoracotomy for oesophageal and lung resection surgery will be discussed in detail. The review will draw on the extensive experimental and clinical literature on the pathogenesis of the acute respiratory distress syndrome (ARDS) and ALI to suggest possible mechanisms of perioperative lung damage. Finally, the therapeutic implications of this hypothesis of post-thoracotomy respiratory complications will be examined.