A case is presented of haemorrhage into a thyroid cyst after endotracheal intubation for an elective nasal operation in a healthy young man. The haemorrhagic cyst compressed the trachea and the patient was taken to the intensive care unit with the endotracheal tube left in situ. Hemithyroidectomy was performed uneventfully two days later. Causes of haemorrhage into thyroid cysts are reviewed.