We have presented a case of unilateral pulmonary oedema which we feel is secondary to obstruction of the right main bronchus during spontaneous respiration. An anode tracheal tube was introduced through a tracheostomy during operation in a man with pre-existing pulmonary and cardiac disease. At the end of the anaesthetic, acute obstruction to ventilation of the right main bronchus developed with the tube still in place and the patient breathing spontaneously. The obstruction was relieved, by repositioning of the tracheal tube, but not before the patient developed right unilateral pulmonary oedema.