Mentosternal fistula is a very rare entity. 70 cases had been reported in the French literature up until 1984. Mentosternal fistula is very different from cyst and fistula of the thyroglossal duct. There is no consensus concerning both pathologically and embryologically, the ethiopathogenesis of mentosternal fistula, but the most widely accepted embryological theory seems to be inclusion of ecto or endodemic material at the time of fusion of the branchial tissues in the cervical midline. Clinical features, in the complete form, are very typical and must be distinguished from thyroglossal duct anomalies. No thyroid exploration is required before the surgical procedure which must be simple and complete.