The endoscopic treatment of chronic oesophageal perforations (more than 18–24 h old) by the application of sodium hydroxide 20 per cent to the edges of the perforation is described. The importance of pleural and mediastinal toilet and the accurate siting of drainage tubes and full expansion of the lung, together with measures for diminishing oral, gastric and bilary secretions from the perforation, are stressed. Five patients who have been treated by this conservative method are presented and the method compared with the more radical surgery advocated by the majority of other surgeons. Copyright © 1979 British Journal of Surgery Society Ltd.