Eighty-six cases of carcinoma of the thyroglossal duct have been reported in the literature, most of these being well-differentiated adenocarcinomas. Three new cases of the latter type are presented. Cases where carcinoma of the thyroglossal duct is suspected should be investigated with fine-needle biopsy, thyroid scintigraphy, skeletal and pulmonary X-ray, determination of TSH, T 3, PBI and blood serum calcium. The treatment of well-differentiated adenocarcinomas is a combination of surgical and medical procedures.