We report a case of mechanical closure of the vocal cords with the laryngeal mask airway ProSeal (PLMA) in an anaesthetized, paralysed 59-yr-old, 88 kg female undergoing lower-limb vascular surgery. Near-complete airway obstruction developed after a size-5 PLMA was inserted and the cuff inflated with 20 ml of air. Fibreoptic inspection revealed that the PLMA was correctly positioned, but the vocal cords were closed. Withdrawal of air from the cuff and/or moving the head and neck into the sniffing position resolved this problem.