A case of Horner's syndrome following a thyroidectomy for a benign multinodular goiter is presented, the literature reviewed, and possible explanations are discussed. Theories to explain this phenomenon include: local trauma to the sympathetic chain during retraction of the carotid sheath, anatomical variations which leave a patient susceptible to damage to the sympathetic chain, postoperative hematoma compressing the sympathetic chain, and ischemic damage to the sympathetic chain.