Ectopic thyroid tissue is the result of abnormal migration of the gland as it travels from the floor of the primitive foregut to its destined pretracheal position. The prevalence of ectopic thyroid tissue ranges between 7%-10%. Patients with ectopic thyroid tissue are usually euthyroid, but can present with signs and symptoms of upper aerodigestive tract obstruction. We report a case in which ectopic mediastinal thyroid tissue was removed surgically because of substernal chest pain. It recurred 9 years later when the patient developed Graves' disease. We propose that the recurrence of the ectopic thyroid tissue was due to the influence of thyroid stimulating immunoglobulins (TSI).