A patient with chronic cough and recent dysphagia was found to have a retrotracheal mass extending into the mediastinum on chest radiography. A computed tomographic scan confirmed a retrotracheal posterosuperior mediastinal lesion which was believed to have a neurogenic origin. A thyroid 131I scan revealed no uptake of tracer in the chest and results of thyroid function tests were normal. A large retrotracheal colloidal nodular goiter was excised through a right thoracotomy. The diagnostic approach and the safety of surgical access by thoracotomy for thyroid lesions in this unusual site are discussed.