To report the relative frequency, natural history, and optimal treatment of thyroglossal duct (TGD) carcinoma. We retrospectively reviewed all cases of TGD carcinoma surgically treated during a 44-year period at a tertiary referral center. The computerized medical records database at Mayo Clinic Rochester was searched for patients who had the diagnosis of TGD carcinoma or TGD cyst carcinoma from 1950 through 1994. Medical records and pathologic specimens of these patients were reviewed. Twelve patients (six male and six female patients), who were 17 to 60 years old (mean, 40), were identified. The frequency of TGD carcinoma among surgically removed TGD cysts was 0.7%. A midline upper neck mass was the initial symptom in all patients. The diagnosis of cancer was made after the Sistrunk procedure in 11 of 12 cases and preoperatively (by fine-needle aspiration biopsy) in only 1 case. All patients had papillary carcinoma. Thyroid involvement was noted in three cases. Nine patients had subtotal or near-total thyroidectomy, and three received postoperative radioactive iodine. After a mean follow-up of 13 years (range, 1 to 38), no patient had a documented local recurrence or distant metastatic involvement, and no tumor-associated mortality was observed. TGD carcinoma is a rare malignant tumor that is usually diagnosed postoperatively. Papillary carcinoma is the most common pathologic finding. The recommended treatment is the Sistrunk procedure followed by near-total or total thyroidectomy by a skilled thyroid surgeon because of the possibility of intrathyroidal foci of cancer. The prognosis is excellent in patients with papillary tumor.