The author experienced a case of lingual thyroid. The patient, 33-year-old woman, was visited to our Dept. with chief complaint of the foreign body sensation of the throat. On physical examination, the oral cavity revealed a tumor mass on the base of the tongue, about 2×105 cm in size, slightly elevated with bluish red color. The scintiscan revealed a functioning thyroid gland on the root of the tongue, measuring 3.0×4.0cm concentrated by RI¹³¹ and there was no concentration of RI¹³¹ in the neck. There was not any symptom or sign due to hyper-or hypothyroidism, therefore no treatment was given to her.