One hundred sixty-three patients undergoing reoperative parathyroidectomy were evaluated before and after operation to determine the incidence of, risk factors for, and morbidity of vocal cord paralysis. These patients were compared to 77 patients undergoing initial parathyroid operation, only one of whom had vocal cord paralysis on postoperative indirect laryngoscopy (1.3%). Preoperative examination of the reoperative patients revealed vocal cord paralysis from initial exploration in 11 patients who were excluded from this study. After re-exploration, 10 patients (6.6%) had vocal cord paralysis, eight unilateral and two bilateral. Right vocal cords were paralyzed twice as often as left. In 90%, vocal cord paralysis was associated with removal or biopsy of an ipsilateral gland. Vocal cord paralysis occurred despite intraoperative visualization of the recurrent laryngeal nerves. Preoperative localization, parathyroid gland pathology, and concomitant thyroidectomy were not associated with increased risk of vocal cord paralysis. Hoarseness was the major symptom. Tracheostomy was required for two patients, one was permanent. One patient was treated for aspiration with a temporary gastrostomy. Nine of 10 patients had return of normal voice quality in an average of 4 months time. On examination 4 years or more after surgery, two of five patients had normal vocal cord motion. The oblique anatomic course of the right recurrent laryngeal nerve may account for the greater frequency of right vocal cord paralysis.