The lingual thyroid is rare in occurrence. The recent discovery and clinical application of sintigram and isotope made progress in the diagnosis and treatment of this anomalous condition. The case is a 24-year-old Korean woman who visited ENT Department of Presbyterian Hospital, Taegu, with chief complaints of voice change and foreign body sensation at the base of tongue. On indirect laryngoscopy, a walnut-sized tumor was found beneath the base of the tongue and it was diagnosed as ""lingual thyroid"" by frozen section. The application of sintigram and I¹³¹ for the confirmation of the diagnosis and for the treatment in this case resulted with an excellent effect. A review of the literature concerning the case was made.