A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was: does re-expansion pulmonary oedema exist? Altogether 233 papers were found using the reported search, of which 13 represented the best evidence to answer the clinical question. The authors, journal, date and country of publication, patient group studied, study type, relevant outcomes and results of these papers are tabulated. We conclude that re-expansion pulmonary oedema (REPO) does occur following re-expansion of a lung in pneumothorax and pleural effusion. The incidence of REPO following pneumothorax and effusion is between 0 and 1% in most studies. The British Thoracic Society guidelines suggest <1.5 l pleural fluid should be drained at a time. Provided no respiratory symptoms occur it is not unreasonable to drain larger volumes to dryness: caution should be taken to avoid high negative intrapleural pressures. Patients who appear to be at higher risk, which may warrant more gradual evacuation, are: those who have had large pneumothoraces; young patients; patients in whom the lung has been down for >7 days; and possibly those who need >3 l of pleural fluid drained.