Soft tissue lateral neck radiography was used in 22 male patients older than 60 yr, to determine the cause of pharyngeal airway obstruction during anaesthesia, before and after insertion of a Guedel airway. In six of the patients, the airway was radiologically and clinically clear with the head in the neutral position. Nine patients showed obstruction of the airway by a “shelf ” of tongue, but seven were cleared clinically by dorsiflexion at the atanto-occipital Joint, and the remaining two by the Esmarch-Heiberg manoeuvre. In four of the 22 patients, the Guedel airway was lodged in the valecula in the neutral position. This was cleared clinically by dorsiflexion at the atanto-occipital Joint in all these patients. In three patients the Guedel airway was obstructed by the epiglottis, but this was cleared by dorsiflexion at the at/anto-occipital Joint in two; in the third patient, the Guedel airway slipped into the vallecula after dorsiflexion at the atanto-occipital joint and remained there despite the Esmarch-Heiberg manoeuvre. There was only one instance in 66 trials of a clinically obstructed airway without an apparent radiological cause. However, there were 10 instances in 66 trials of a clinically clear airway with an apparent radiological cause for obstruction.