PRECISELY regulated movements of the vocal folds (cords) are known to occur during respiration, swallowing and phonation in most mammals, including man1. That such movements must involve integrated reflex adjustments of the tone of the laryngeal muscles is apparent; and, by analogy with the situation in the limbs, the source of such reflex regulation has usually been sought in the laryngeal muscles themselves (or in the laryngeal mucosa). There is, however, no agreement on whether appropriate receptor nerve endings are present in the laryngeal muscles2,3; and attempts to record afferent proprioceptive discharges from the nerves supplying the laryngeal muscles have failed to demonstrate them4. Nevertheless, direct electrical stimulation of afferent fibres in the laryngeal nerves does produce reflex alterations in the tone of laryngeal muscles4,5.