Clinical observation was made on 40 cases of thyroglossal duct cyst and fistula with brief review of literature. The authers have performed a clinical study on the thyroglossal duct cysts which were diagnosed and treated surgically in the Department of Otolaryngology of Kyung Hee University from 1971 to 1985. The following results were obtained : 1) Most cases were under 20 years old(75%) and sex incidence revealed 23 in male 17 in female. 2) The types were cyst in 34 cases and fistula in 6 cases. 3) The prominent symptoms and signs were soft, frequently fluctuated cystic mass and chronically pus discharged fistula located on just below the hyoid bone, in midline of the neck. 4) 7 cases were recurred and 4 cases were recurred twice, at the time of first visit. 5) There were 2 cases of having connection with the thyroid gland which were identified grossly on the operation field. 6) Thyroid scan was done in 9 cases preoperatively and revealed no abnormality. 7) The entire cases were operated according to the Sistrunk procedure under the general anesthesia. 8) There was no recurrence and complication except three cases of wound infection.