INJURY to the recurrent laryngeal nerve is one of the chief hazards of thyroid surgery. An accurate, anatomic knowledge of the course and variations of this nerve is essential if vocal cord palsy is to be avoided. Berlin1 has stated that it is "the variability rather than the vulnerability" of this nerve which is responsible for the frequency of serious injury. Clinical improvement in vocal cord paralysis following electrical stimulation therapy2 led Weeks and Hinton3 to the hypothesis that many nerves had extralaryngeal divisions and that the nerve supply to the laryngeal muscles on the affected side was frequently not completely interrupted but rather so reduced by the division of one branch that only when assisted by artificial stimulation could it regain motor control over the injured muscles. To explore this possibility, these investigators dissected 28 cadavers and found that 78 per cent, or 43, of the